I'm sure the graphics looking better all depends on the developer too - of course some devices just look better than others, even between only Palm type products. If the developer works mainly on the PPC version and just throws together a Palm one, or vice versa, then of course one will be better than the other.
I personally only have a Palm as I have limited funds and I just bought my T5

I'm very happy with it and though I'm very curious about PPC and will probably pick one up eventually, I think they both have their perks and down sides and I've been nothing but pleased with my Palm and the game functions and as with ANY electronics, some brands are just better than others - so there could in comparison be a Palm that BLOWS AWAY a PPC - and again, vice versa

It's all personal preference on selection, features, how it looks, what types of products are available for it, etc. Like I'm a die hard Nintendo fan because I love Mario stuff and I grew up with that brand of games - but I'm sure that other game platforms might play faster or look better but I don't care - because I love what I got!
So in summary - find something you enjoy and LOVE IT. Or, save up and buy one of each - lol.
I'm babbling.