A:Answer Alvaro,
It all depends on your intended use. I own both HP 50 G and Prime as well as others, 48GX, 42S, 35S, 15S, etc. Do you need the graphing capabilities? Are you going to write lots of programs (RPL vs HPPL)? I prefer the keyboard of Prime over 50 G, and for simple calculator like tasks, 35S works well. I have created some custom apps for the Prime to solve typical engineering problems I encounter every day. I would recommend you go here for more help: http://www.hpmuseum.org/forum/
