Hi. I am currently using a TI-89 Titanium calculator, but I have been thinking of getting a new HP Calculator because I have a problem with my current calculator. Before I change from TI to HP, I have a few questions about HP calculators:

1. What is the difference bewteen the HP 48II, 49+ and 50?

2. What is the difference between a HP 50g and a TI 89 Titanium?

3. I read that SD cards can be used for memory on a HP 50g. Can any SD card be used, or do I have to buy a HP one.

4. I read that people have had problems with keys "getting loose" on some HP calculators. Could anyone explain this problem to me, and which calculators are affected by this?

Thanks for your help!