Well, you can break people's guards, and I personally think that the burst system is superior in Blazblue.
Fatal counters are also kinda neat.
I also prefer the character specific quirks in Blazblue over Guilty Gear (except for Chipp's invis Q_Q. I'm gonna miss that). Tager's magnetism, Hakumen's self filling magatama bar, and Arakune's curse meter > Venom's pool balls and Testamet's little traps imo.
Overall though GG is a better game. But BB isn't complete trash and I like a couple characters in it (as opposed to the...two I liked in GG, one of which was a trash character).
I actually prefer GG's burst system. BB's is too limiting, IMO.
The thing I like most about BB is that the Oki game is deeper. There's not just the question of if they're going to tech, or what they're going to do after their wake-up. There's also the question of whether they're going to roll, or in what direction.
Overall, I'd say GG is better balanced, but BB feels more polished, particularly in the sound mixing sector. I also like BB's animation style better, as well as better overall character personalities. So I'd say BB is a better game all told, but GG has more lasting appeal as a balanced fighter.