Okay, I too have pondered this issue
Regarding how well they work . . . Bummis and ProRaps, as far as I'm concerned, both work pretty much the same once you get them on and everything tucked into place. They both hold it in very well.
However, here are the 'lacking' area of both IMO:Bummis
1. If diaper is saturated underneath, it will wick to the leg casings on the thigh. I'm not sure why they didn't make the leg casings the same as the Whisper Pants, but it is a soft poly knit fabric that just soaks up moisture if the diaper is significantly wet.
2. Bummis does not seem to 'expand' to cover as much as the ProRaps.
3. Bummis do not have gussets.ProRaps
1. ProRaps DO NOT HAVE velcro foldbacks . . . which bug me.
2. ProRaps' tabs are a bit wider than I like and it scrapes on Kenny's Buddha belly.
3. ProRaps look dingy fast - the outer material just doesn't hold up (as in - remain looking nice) for the amt. of time Bummis do.
What do I prefer?
Bummis. I wish they had gussets, but they are just the 'hardier' choice for us. Plus, I really like the thinner tabs.