I got pissed at Mathematica because of the way they do licensing so I stopped using it completely. I would use Mathematica every so often and pretty much ever time I wanted to use it, the program would tell me a needed to get a new license.... Also, Sage is faster than Mathematica. As for MAGMA vs Sage, I am sure that MAGMA does things that Sage doesn't but so far isn't anything I need to do. Even though Rice has a license for MAGMA at this time, I would rather not be tied to a software program that is so costly. (Sage was developed as an open source alternative to MAGMA.)