Lotsa good suggestions already. Abena M4s/L4s have a really nice fit for me (everyone's body proportions and shape is different so this may or may not be the case for you) and I do like the medical graphics they use.
I haven't tried Tranquility ATNs in a while, but remember liking them and being pretty impressed for the price. But there are definitely more absorbent and higher quality diapers, but they also tend to cost more.
NorthShore Megamaxxes are really high quality all white super absorbent diapers with crazy strong tapes.
Trests are also all white extremely absorbent high quality diapers. Probably higher capacity than MegaMaxxes, but their tapes, while still good, aren't as good as MegaMaxxes. Trests are also ridiculously expensive, at least atm, if they adjust their pricing or make them available in discounted case/half case quantities then that'd make them a bit more reasonable.
Chances are any diaper from any ABDL diaper company will probably be more absorbent than a Tranquility ATN and many ABDL diapers sell all white versions of some of their other diapers that normally have prints on them.
I haven't tried them yet but NappiesRUs and Tykables have started selling their Str8Up all white diapers which I imagine are probably more absorbent than Tranquilities as well.
ABU Simple-ultra's are their Peekabu diapers without the landing zone graphic (their Simples are less absorbent versions of their Ultras).
Rearz InControl with the adhesive tapes is I believe the same as their Safari
Bambino has the Bianco Ultra Stretch which appears to be their Magnifico shell. The Magnifico doesn't have the highest capacity compared to some other diapers though. And I think the Bambino Bianco is their Bellisimo shell.
BetterDry diapers are Crinklz shells without the graphics.
LittleForBig has their ABDry White diapers. I'm not super familiar with L4B, but I've heard good things about them and their quality. I think they use the same shell for all their diapers, but only change the graphics, but I could be mistaken.
Personally, I prefer diapers that have landing zones for the tapes so they aren't adhering directly to the shell. This can make readjusting better but I also find that tapes tend to adhere more strongly to a landing zone material instead of the soft plastic shell. As a result of this, they tend to have a snugger more secure fit and are less prone to sagging and stretching and loosening as you wear them for longer which helps them reach a higher capacity without leaking.