Bearing in mind that I have only ever seen pictures of these, never actually seen a real one what are they both like.
As we'd all probably agree, cases are
very subjective. One person's junk is another person's holy grail. But I personally think the Wave Master is the nicest case I've ever seen or touched. Fit and finish are outstanding (in black or silver), and the one I drooled over (figuratively speaking) felt more solid than any other computer case I've ever seen.
One thing I don't like is the top-mounted ports, but Cooler Master makes an adapter kit that lets you convert that space into a blowhole for a fan. You can then purchase an inexpensive 5.25" bay with USB/Firewire/audio ports (or whatever) from FrontX, Inwin, Enermax or whoever and have your ports on the front panel with your drives. This is what I intend to do when I get one of these cases.
Oh, and it comes with sleeve-bearing intake fans on the front (what were they thinking?). I also intend to replace those with some Panaflo 12L's or PC Power and Cooling Silencer 80 mm fans (or just disconnect the stock fans and not use intake fans at all). No case is perfect, but this one comes about as close as any I've seen. Some people don't like a door on the front of a case, but I don't mind at all.
Re the casters, you can buy some small casters at Home Depot (or whatever comparable home improvement stores you have there in the UK) and probably just screw them into the bottom of the case (assuming they won't hit anything vital on the inside!). That's what I intend to do as I too like a case that's easy to roll on the floor.
To each his own. I like these cases and want one.
Good luck, mate.
PS: If you're interested,
here's a reasonably decent review (if you haven't seen it already). Oh, and there's a line in this review about the black case not being anodized aluminum on the inside. I called Cooler Master about this awhile back and they assured me that the reviewer was incorrect -- the inside of the both the silver and black cases is anodized aluminum according to CM.