The main difference between the two (other than the RPN which I don't care much about as I am already used to using a TI-83 which doesn't have RPN) is that the HP is powerful, and the TI has more 3rd Party support. Of that though, the things I care about most is that you can expand the memory of the HP 50G with an SD card, and that TI-89 has many more 3rd programs than the HP 50G. So basically, I'm wondering a few things. What is the maximum recognizable of space on the SD card? If I put a 4GB card in the HP 50G would it recognize 4GB? I wouldn't use 4GB, infact, I don't see how I'd use more than a few extra MB, but I was just wondering, how much could be recognized? Is there a way that TI-89 programs can be run on an HP 50G? It probably sounds stupid, but I was thinking maybe there's some way to install something that allows it to run the programs of other codes. Will I really need more than the space aviable on a TI-89? I'd like to have a few games, and some programs for certin subjects and some notes and stuff, but I won't have huge amounts of stuff. And I could rotate what I have on there, but 2.7MB just doesn't sound like a whole lot.