With modern bows and arrow speeds as they are, I don't think it will matter more than an inch at best.
Practice at 20 and 25 yrds with the slide set to both 20 and 25 yrds. I'll bet there isn't enough difference to worry about, like I said, probably not more than an inch.
I don't have a 20 yrd pin. I have 25, 35, and 45 yard pins. In reality, I could use my 35 yrd pin and simply hit slightly high at anything under and slightly low out to 40 or so.
I have actually considered removing all pins except one set at 30 yards.
The main reason I haven't is that most deer I've shot were 10-15 yards, and I don't want to hit too high.