There's a lot of all white to choose from right now, so it probably comes down more to what features you want.
Best value right now I'd have to say is the MyDiaper white. Features are great, capacity is surprisingly high, and cost is comparatively low.
Best value / cheapest high capacity all white right now is probably the A+ when on sale.
If you're in europe, betterdry are one of your best options. Overall quality is very high, but they get expensive outside europe.
Highest capacity (among those I've tried) are the ABU and Rears Simple and Basics. If you want a THICK, high quality diaper, and cost isn't a big deal, these are the two to look at.
I haven't tried Fabine's newest offering ("gold"?) but it may be a contender for premium white padding.