I read many moons ago that slower swingspeeds need firmer covers; higher swingspeeds need softer covers.
Or, replace the word "need" with "should use".
I'll tell you about a stupid long ball, and iirc, it's a legal one(as they claim). Slazenger "Money" ball. 65 comp, 392 dimples, ionomer cover. Doesn't feel soft at all(to me). 2 doz. for around $20, or so. Think they only come in white though. Played 2 rounds so far using them. I'm ready for WLDC qualifiers!!😉