I'm guessing it's you. Sorry.
I've got both and I have no problem winning on either. In fact, I've even managed that "Win a match without dying" trophy on both.
Yeah, keep trying. Practice makes you better.
Pick someone who "feels" right for you... then find the best way to generate AP with them.
The last step is figuring out how to best exploit your supers. Can you keep cleaning up with level 1? Should you save til level 3? Or a mix of 1 and 2. (Example, I pretty much store to level 3 with Kratos, use level 2 exclusively with Spike, while Raiden and Dante I stick with mostly level 1).
Once you get better, you'll want to start working in throws and dodges. Throws work to drain XP from opponents, so it's useful against people who are storing to get to level 3.