I can't really judge Injustice considering I have 0 MU experience, have never played an actual human being before (two beginners I played while trying out online once don't count), and thus, have not experienced the "BS" others have.
However, based on practice mode and playing the AI countless times, I will say I prefer the following mechanics over ones in MK9:
1. Properties of dashes - I know a lot of people wish they were cancelable. I dunno whether making them so would negatively or positively impact the game, but I do know that they have an evasive property that makes AAs and even poking unnecessary a lot of times. Essentially, it's like a universal Smoke Away (minus the anti-projectile ability) that shouldn't be spammed, and I love it.
2. Reversals and push-block - In this game, there's an alternative way to deal with pressure aside from GUESSING when to poke out. I fucking hate Johnny Cage, Kabal, and whoever else had bullshit pressure like that. Mind you, I'm speaking out of my ass since, like I said, I have 0 MU experience, and there may be a character like them here (Doomsday?). I believe if you guess right when people are pressuring, you can also simply dash back. Again, dash is awesome.
3. Clash system - I like it more than breakers. There were some issues with MK9 breakers, such as certain characters actually being able to combo or perform set-ups after them (mainly, Cyrax and Smoke, but everyone could D3/D4 if they broke in the air). But besides this, some characters built meter too fast, and could breaker anytime you approached them (Kabal). I like the thought of a limited number of breakers. I don't think there should only be one breaker in MK10, but maybe three per entire matches (1 per round). Obviously, they would have to do away with bullshit Cage-like pressure, and 100% resets, but I think they learned their lesson.
What I like more about MK9:
1. Anti-airing - If I'm not mistaken, many characters in Injustice do not have AAs because they compensate in other ways, whereas characters like Aquaman have designs that make AAing a necessity. So in the end, it all comes down to a balancing question. However, it still bugs me that this game encourages jump-ins so much. In MK9, you really needed an excellent amount of spacing and precision to AA properly, and that form of strategy is really appealing, as well as incredibly satisfying when you execute correctly. In Injustice, you MAY be able to AA, but good luck not getting bodied instead.
2. D4 - Excluding Mileena and Sonya. I like this long ranged, hit advantage giving (unless you're Scorpion or CSZ) poke. It adds an extra amount of depth to the game imo, especially if your character doesn't have a low starter.
That's all I can think of atm. I'm not going to say whether I prefer the block button or not, or the physics of one game over the other because these are just vital components of what make the games....what they are. It's like saying I like Street Fighter more because it's not Tekken.
.
