Im more of a GTA fan than SR. I played both. Didnt play SR4 yet. I think GTA is more realistic while SR4 is just for shetz and giggles.
Well no offense, but duhh. Lol. I mean that's what they go for and they make no secret about it. In fact, in SR4 they manage to take that non-seriousness comedy goofiness to another level even. Too much it seems in fact for even myself. At least not to consider buying it until or unless it's extremely cheap & even then that's no guarantee.
The main thing some people like about Saints over GTA is it tends to have more room for customization & creativity. It has its positives & negatives perhaps like most & almost any, but there are some goodies such as the few I mentioned & several more it offers differentiated from GTA that make it fun for many in its own right as well.