The Caen wet will work well in 8GB (loaded in 16 bit), but the surround version needs more. I'm using it in 12GB, with the surround samples loaded in mono. Although the effect of the surround version is wonderful, I prefer to practise with just the wet, and I actually like the more direct effect it gives.
Whilst you can, of course, alter the voicing for your setup, I don't find the out-of-the-box instrument at all unusable.
I don't have the Metz, but I have played it. It's wonderful, but just a bit too indirect for me. In fact, for serious practice, I often use the St George's Casavant with some reverb - very precise and analytical!
In the end, they're great sample sets, and it's probably more a matter of taste than anything else.