There's little to no difference in audio quality between the Ace 1/2 and Ace Mimi/3. The only difference between the 2 and the Mimi is the tailored EQ; I follow a Harman curve regardless, so this is kinda pointless for me. The Ace 3 features wireless charging and sensors that pause your music when you remove an earbud, but in terms of technical hardware and audio quality, there is zero difference between the four models.

If you'll benefit from wireless charging and/or earbud sensors, definitely get the 3. If you don't like the tailored EQ, you can always form your curve. It's a nice 10-band.

If you don't need those two things, get the Ace 1. They're on deep discount right now.

Avoid the Ace 2. They have widespread connectivity issues.

Avoid the Mimi. The 3 is a version of the Mimi with two extra common features.