These are the two covers I have used most.
Proraps are a good workhorse kind of cover. They're not in the least pretty, the fabric feels less nice, and the Velcro is big, and tends to gather fuzz and roll back with time. They do the job well, though, and the leg gussets are fabulous at keeping messes in. And the big Velcro means that they're pretty adjustable for different shapes and sizes of baby. But as baby starts to outgrow each size, you can often get scratches from the Velcro. I have had a lot of chafing and red marks with this cover. Also, you can use them many times before they need washing, unless they get poop on them, because you can just wipe out the inside and air them, so you can get away with fewer covers and less washing. They're roomier through the rear, which makes doubling up for nighttime or a heavy wetter easier. The newborn size is very small, so that it really fits the baby well.
Bummis are definitely of a higher quality, in my opinion. They are cuter, the fabric is nicer, and the aplix fastener is nicer-- it doesn't pick up as much lint, and it has the fold-back tabs for washing. I have had fewer red marks with these. They are a little less adjustable, and they lack the leg gussets, but they hold in the mess just fine. They do have the inner fabric, which tends to pick up urine odors after only one or two uses, so you wind up washing more. They're not as roomy in the rear, which is good if you're going to trifold instead of pinning, as it keeps the diaper in place better. The newborn size is slightly bigger, so that it fits longer. I think you get less use out of each size with this cover, because it's trimmer-- DD seems like she grows out of these faster. It's harder to double-diaper, also.
Honestly, if money is not an object, I say go for the Bummis and just expect to wash more often. But if you go for the Proraps, you're still getting a cover that will do the job well.