[0]: https://en.wikipedia.org/wiki/List_of_computer_algebra_systems
Obviously, Mathematica is the leader in academia generally, as far as I can tell, but I personally haven't had good experiences with it myself, but I also have a strong preference for free software, so I haven't tried to hard to get used to it.
I ask because I suspect, like cameras, the best computer algebra system is the one you have with you...or rather what matters is using one not shopping for one.
Anyway, there's Mathematica and everything else when it come to optimizing initial choice.
But I could be wrong. Good luck.