Size isn't everything, young Padawan - wolverine > cow even if it's smaller.
And thus I can segue neatly into my next point, which is that in SWG the pets were absolutely freaking huuuuuge (or could be) and -- I'm going to be blunt here -- irritated the hell out of everyone but a tiny minority of people who like huge pets. Seriously. The cool factor may be high, but the "jeez get that thing's butt outta my face!" factor is higher.
Now, a little bigger - yeah, they could probably stand to be that, at least the wolf & bear. I think the phoenix pet looks pretty neat just as it is.