I want to say that the reason RASHBAL treated Rabi Yishamael bar Aba differently than Rabi Zeira treated Rabin bar Chinena is this:
Rashbal had a low opinion of Babylonians (eretz chashucha...limud chashuch etc.) - but since Rabi Yishmael was from E"Y (Rabi, not Rav) - he was mekabel him.
Rabi Zeira, who davened to forget his learning of Bavel, didn't want to learn from a Bavlai once he came to E"Y (and we know here this is after his aliyah, since he's called Rabi) - (even if the teaching itself came from RIBAL) and so dismissed him.
Tuvya Marcus, Jerusalem, Israel
I would argue that it would not make a difference to Reish Lakish and Rebbi Zeira who said this Halachah, because we have a principle of "Kabel Es ha'Emes mi'Mi she'Amarah" -- "If something is true, accept it whoever says it." (See the Introduction of the Rambam to Pirkei Avos, "the Introduction to the Eight Chapters," "Shema ha'Emes mi'Mi she'Amaro.")
In fact, both Reish Lakish and Rebbi Zeira accepted what was said in the name of Rebbi Yehoshua ben Levi, but the difference was in the way they accepted it. Reish Lakish praised immediately the Chacham who said it, while Rebbi Zeira accepted it quietly without praise, and then when it was repeated he criticized the repetition. But they both agreed with the Halachah that they heard.
Kol Tuv,
Dovid Bloom