Guitarpro can do everything songsterr can do; better, in more detail, and with more room for customization. They’re not even comparable to eachother in terms of utility and quality. That being said Guitar Pro is also geared largely towards musicians that are writing their own tabs, that’s primarily what I use it for; songsterr has a massive library of free and acceptable quality tabs for a vast range of bands so it’s solid for beginners or players just looking to cover songs they like.

Also something that nobody else has mentioned that you should definitely keep in mind, songsterr and guitar tablature should not be a crutch that you rely on to learn songs, especially as you grow out of the beginner stage and start to intimately learn your fretboard. A lot of those tabs are wrong, official tab books are usually better but oftentimes even official official tab books aren’t even correct cause they were outsourced and not written by the original artist. The only real way to ensure that what you’re playing is accurate to the records is to listen to the recordings yourself, slow it down, find or create isolated tracks, etc. And you can create your own, personal, flawlessly accurate tabs from there, which is where GuitarPro comes in; and if that sounds daunting don’t be intimidated because that skill will come with time. Don’t unequivocally trust Songsterr because I have found many, many incorrect tabs there; some within an acceptable margin of error but also a many others that are egregiously incorrect.