About Bummis
I've been using Bummis super snap for six and a half years on four kids. It's crumby that they don't offer them in colours and prints, but if you're planning to run a diaper service they are a very long-lasting cover.
The elastics hold up extremely well. I wash in water that's just below boiling. The cycle takes over two hours to run, and our washer spins at 1600 rpm. The elastic on the Bummis holds up the longest of any diaper product I've ever owned.
The PUL in Bummis is sandwiched. I believe this is to make them last longer since it protects the PUL from ripping when it de-laminates. I'm not sure if this is true, but I've also heard that PUL de-laminates faster on colours and prints than plain white. Bummis covers still work fine once de-lamination happens, but they don't feel as nice and from a diaper service I'd probably expect it to still be laminated. I haven't been able to confirm the thing about colours and prints, but it seems to be true from my experience.
Also, the one time I had a snap go bad Bummis company replaced the cover immediately. They didn't even ask how old the diaper was. Apparently their snaps are supposed to just last forever.
Since you're looking to run a diaper service I think you want to look for tough, long wearing products. A lot of people are happy with how well a product does when they use it for the duration of one or two kids, but I think you might want to seek out the most long lasting stuff available.
I only know the details of one diaper service well enough to know what products they use, but they use plain Bummis white covers. Have you looked around to see what other diapers services are using?
The other problem with fancy covers is that not all people like all colours and prints. There's a reason real estate agents tell people to paint their house neutral colours when they're trying to sell. And even if you do like a colour or a print, they can sometimes be a pain when they show through clothes. Worrying about which customers want what in terms of colours could make things a lot more complicated for you.