So for present purposes, I will use a much smaller substitute, which can hardly be accused of any partiality to Standard Arabic: namely, a selection from Said Akl's Roomyo w Julyeet, which I was lucky enough to run into at an Oxfam a few years ago. I picked a well-known section of the play whose language seemed relatively simple, with little or no visible Standard Arabic influence - the lines starting from "Romeo, Romeo, wherefore art thou Romeo?" (p. 62), including Romeo's reply and Juliet's reply to him (finishing on the second line of p. 63) - and counted morpheme frequencies (retaining his eccentric orthography). The 26 morphemes that occurred more than once account for about two-thirds of the selection, so looking at their etymologies gives us the maximum of information for the minimum of effort - and here they are. Only those that are unambiguously Arabic or unambiguously Aramaic are relevant to our purpose; the rest may be dismissed as "confounding factors":
- w(e) و "and" (11 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- b(e)- / m- بـ٬ مـ [marker of the indicative imperfect] (10 occurrences): Innovative. This form is found as such neither in Classical Arabic nor in Aramaic, and its etymology poses some difficulties; if you know of any convincing work on this, let me know in the comments.
- -aq ـك "you m. sg. oblique" (9 occurrences): Arabic. Both Aramaic and Arabic have cognates of this, but in Aramaic the consonant has changed to kh, whereas Levantine - like Arabic - has kept the original k.
- ¢esm اسم "name" (6 occurrences): Arabic. Both Aramaic and Arabic have cognates of this, but in Aramaic the consonant is sh, whereas in Levantine - as in Arabic - it's s. (There is controversy over which value is original.)
- la "no, not, neither... nor" (5 occurrences): "Confounding". The form is shared identically by Arabic and Aramaic; the usage is actually closer to Arabic (where it negates verbs only in the imperfect and the negative imperative) than to Aramaic (where it negates verbs in all tenses), but we'll score it as shared.
- -u / -h / -vowel length (depending on context) ـه "him, his" (5 occurrences): Arabic. Aramaic -eh could explain the h form and the vowel length form, but the -u can be satisfactorily derived only from Arabic -hu.
- quun كون "be" (4 occurrences): "Confounding". In reality this is much more likely to be Arabic, since the normal Aramaic root for "be" is hwy, but kwn is attested in this sense in Aramaic too.
- men من "from" (4 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- ḍall ضل "remain" (4 occurrences): Arabic. There is no Aramaic source for emphatic D.
- (e)l الـ
- "the" (4 occurrences): Arabic. (Aramaic originally used suffixed -aa, which later lost its definite sense.)
- [relative marker] (3 occurrences): Innovative, but based on extending the functions of the Arabic definite article, and probably on shortening a form similar to Classical Arabic alladhii, which it resembles rather more than the Aramaic relative marker dh-.)
- ¢ent انت "you (m. sg.)" (3 occurrences): Arabic. In Aramaic, the n disappeared, assimilated to the following t.
- ma ما "not" (3 occurrences): Arabic. In Aramaic, maa is never used as a negator.
- law لو "if" (3 occurrences): Arabic. (Aramaic does not generally use this, but where traces of a cognate are found, as in some frozen combinations, it takes the form luu, not law.)
- cu شو "what?" (3 occurrences): Original, from Arabic. Found as such neither in Arabic nor in Aramaic, but its generally accepted etymology is Arabic, from a contraction of أي شي هو "what thing is it?".
- sammi "name (v.)" (3 occurrences): Arabic, for the same reason as esm above.
- e- / Ø- أـ [first person singular subject marker] (3 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- t- تـ [second person masculine singular subject marker] (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- -ni ـني "me" (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- -a ـا "her" (2 occurrences): "Confounding". At first sight the loss of the h makes it appear closer to Aramaic than to Classical Arabic - but the h was also lost in -u "him", which cannot be explained as Aramaic.
- -t ـت [feminine singular construct state marker]: "Confounding". The form is compatible with Arabic or Aramaic origins (Aramaic had th, but we would expect that to be turned back into t, since Levantine has no interdentals.) The function straightforwardly existed in Aramaic; in Classical Arabic, it did not, but the pre-pausal pronunciation of -at- as -ah provides an obvious source for it to develop from, and indeed it exists in practically all modern dialects (including those of the Arabian peninsula). If you're feeling really generous, though, you might ignore the latter fact and award this one to Aramaic.
- ¢ana أنا "I" (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- hu هو "he" (2 occurrences): "Confounding". At first sight the Aramaic form huu is closer than Classical Arabic huwa, but loss of final vowels is regular in Levantine Arabic, so you would expect huwa to become hu anyway.
- ya يا "oh" (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- ¢aw أو "or" (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- xebb حب "love" (2 occurrences): "Confounding". Shared by Arabic and Aramaic in effectively identical form.
- jez¢ جزء "part" (2 occurrences): Arabic. I haven't noticed an Aramaic cognate, but even if there is one, the palatalisation of the j (from original g) marks it as Arabic.
So, out of these 26 items - which together account for 107 out of the 161 morphemes in this selection - 10 are unambiguously Arabic (accounting for 46 morphemes), and none are unambiguously Aramaic. 15 items (accounting for 91 of the morphemes) could equally well be Arabic or Aramaic, and as such are irrelevant to determining which one predominates within Lebanese Arabic. (If you decide to be really generous to Aramaic, you might shift -a, hu, and -t to the Aramaic column, accounting for a grand total of 6 morphemes versus Arabic's 46.) The remaining single item, the imperfect prefix b-, is a later innovation whose history is unclear; even if someone found an Aramaic etymology for it and added it to all the unlikely cases mentioned, the ratio of "content ⊂ Arabic & ⊄ Aramaic" to "content ⊂ Aramaic & ⊄ Arabic" for this list would still be about 3:1. On a less generous and more plausible calculation, it's infinite (46:0). Either way, by this criterion, too, Levantine is Arabic, not Aramaic.
If you pick a long enough text, of course, you will eventually find an Aramaic loan or two. There are quite a few Aramaic loans in Levantine Arabic, depending on the dialect, and they must really stand out to a Levantine speaker studying Aramaic. But even in the most heavily Aramaic-influenced dialects, they occur far less frequently than unambiguously Arabic forms. While historical linguists' usual definition of language origin does not rely on any explicit frequency criteria, in all the cases I've seen, the most frequent source of vocabulary by token count for a sufficiently large text turns out to be what historical linguists would consider as that language's parent. In Levantine Arabic the effect is even stronger, since not only is the basic vocabulary of Arabic origin, so is most of the learned vocabulary.
Now, after all those calculations, I'm sure you're eager to read the lovers' dialogue, so here it is:
جلييت: يا روميو! يا روميو! ليش انت روميو؟
نكور بيك٬ ورفود اسمك٬
أو٬ إذا ما بدك٬ حلوف إنك بتحبني
وأنا ببطل كون من عايلت كابيولت.
روميو: بضل عم بسمعا
أو بحكي معا؟
جلييت: إسمك بس عدوي.
انت، بتضل انت زاتك٬ ولو ما كنت منتغيو.
و شو المنتغيو؟ لا هو إيد ولا إجر
ولا دراع ولا وج ولا أي جزء
من جسم الإنسان؟ آه، كون اسم تاني!
و شو فيه الاسم؟ ال منسميه ورد
لو شو ما سمينا بتضل ريحتو حلوة،
و هيك روميو، لو ما تسمى روميو
كان بيضل محتفظ بهالكمال المحبوب
ال بيملكو بدون عيب. يا روميو، تجرد من اسمك،
ومقابل اسمك ال هو مش جزء منك،
خدني أنا كلي!
And in the original orthography: