Super Smash Bros for me personally.

Overall smash is it for me. And that looks to continue with the new ones coming out.

Mario Kart 64 Mario Kart: Double Dash!! > Melee
Mario Kart Wii > Brawl
Mario Kart 7

I prefer to have Super Smash Kart, though.

Karts flying off the track, everywhere!

Both are awesome but I like Smash Bros a little bit more.

Super Smash Bros. for me. While I do like Mario Kart (especially DS), Super Smash Bros. is my 2nd favourite franchise of all time.

To quote our lord and saviour Rolstoppable:

"Smash is trash and Kart is smart"

Seriously though, I can't stand Smash Bros, but I adore the better enties of the Kart series.

I used to not think too highly of the Smash Bros. series as well. That was before I rediscovered its competitive factor (which Brawl subconsciously made me forget):

Still, if that's not your thing I can understand that.

Mario Kart, it's the pinnacle of arcade racers.
Smash Bros is not at the top of fighters or platformers. It's a good combination of both but still has its flaws.

For those saying that Brawl was better than Kart Wii, you must have forgotten what a shit-ass mess Brawl's online was.

Kinda hard to judge a game that hasn't released yet, but it's got a lot to live up to be able to be compared to Kart 8.