I can't/won't give a comparison between the two because, though I've read about both, I haven't seen any articles that compare the two. Also, I don't own either one so I'm not qualified. I'm throwing my two cents in cause I just went thru this decison, and I chose the Pioneer. The reason is because despite any reviews I've read, I seriously don't think I'd notice the performance difference if there even is one. And even if I did, I can't image it being that great. Plus I'm upgrading from a four year old cd-rom, so ANY performance increase is gonna make me happy. And last but not least, I wanted the slot load, I'm not ashamed to admit that I think it's cool, and novelty or not, I want it.
Get what you want man, you only live once!
Forgot to mention, the prices are almost exactly the same (in Lite-On's favor).