ZXA > ZX in all respects.
I don't have a Magical Talking Whatever and I don't have an Uppercut, and you may know your official canon, but Megaman ZX was far better than anything ZXA ever threw at us.
Granted, neither has any real replay value as far as the main game goes (Omega's fun to challenge, and it's worth going through 2 times for a Model X run, only in ZX), but ZX did everything better. Music, stage design, story, everything.
ZXA's Weapon Bar, "vague answers" story, gimmicked boss abilities, useless sidequest rewards, mediocre music and graphics, and general lack of IP enhancement and protection in the form of well thought-out cast and asset management (i.e. changing the 4 Guardians' original designs completely...), made ZXA one of the worst Megaman games Capcom ever put out, right there with X6 (which also destroyed the rightful conclusion to the X series, X5).
Now, the core design of X6 is not okay. The camera shows even less of what you need to see than X4 and X5 did, there's the whole Zero's diving attack ordeal, the Z-Saber completely obliterates the final boss, you have to exit stages to switch inane Parts, and did you SEE Blaze Heatnix's stage?! Heck, X's use of the Z-Saber is dismal, at best. He should have either had more power in that one shot, or had Zero's 3-stage attack. The Blade and Shadow armors are fan-level creations.
And Model X is not overpowered. Model X has range, that's it. Both X and ZX have the same very powerful spiral charged shot ala X2, it's just a matter of range. There are some players who make better use of the charged Saber Slam than veterans/Model X users manage that first, comparatively weaker charged buster. In fact, depending on your playstyle, you get more damage out of having ZX's 2 weapons as compared to X's 1 weapon.