I was looking for free alternatives to Magma to perform number theory computations, such as modular, factorization, etc. and I've found GAP and Pari.
What's the difference between them? Any other advise instead?
New: Sage has a lot of features but it has two drawbacks: It's made with many different applications, great applications but independent, with few features, not properly merged on a single one. Each application has its commands, format...
And it's OK for Linux users but for Windows users has to be run virtualized, much slower.
I've found that the difference is that SAGE is better for abstract algebra problems and PARI for big number arithmetic.