Which is better? Definitely Saints Row IV! It's fun and hilarious. Sure, GTA has high production values, yadda yadda. Saints Row simply has fun with the formula and will literally make you lol repeatedly.
My specific bitch about GTA4 is: let's say you accept a mission, drive all the way there to start it (which could be a long way in the latter parts of the game), then die - the game will make you get back there and start it all over from the beginning. No mid-mission checkpoints. Minor gripes include the fact that the main character talks like Ren from Ren & Stimpy and overall, imo the GTA games are played out. They just aren't fun really. I even sat through GTA5 and though it was more interesting and fixed a few issues, it has gotten old.
Saints Row, on the other hand, a blast from start to finish. Best $5 you'll ever spend. Fun, silly, ridiculous - I'll play any Saints Row games that come out in the future but GTA? Nah, I'm done.