I have both and each is nice for anal play. The Acute gets used more than the Curve, I just like the feel of the Acute better.
The Curve has a matte finish and holds the lube better than the Acute, but once your anus gets properly lubricated they both perform equally well. The Curve is easier for a partner to hold due to the base but I like the Acute's base for solo use.
Can't help much on harness use, but I would guess the Curve would stay better because of the thicker base. Although, I have read that the Acute works good too.