Truthfully, you've selected (imho) the two best balls on the market: it's impossible to go wrong with either. Personally, I use Dunlop Grand Prix, simply because it's available where I live. Having said this, the Slaz. Wimbledon is also siad to be a superb ball.
i use both and theyr almost identical,
i figure its because they are made form the same company(both owned by same bigger company), so theyr made in the same factory, just labeled dif.,
but honestly, i couldnt even tell the dif.