Well, taste is a very personal thing, in my case and in my room, I also prefer a gray screen, much like my wife.Generally speaking, aesthetically, white screens always look better in rooms than darker gray screens just from aesthetics. That is my opinion though, I'm not a decorator, to me gray screens look ugly. If you have an aesthetics issue though, you need an electric screen. Electric screens are much much better for that.
CineGrey 5D is a decent material, I have seen it both in a showroom and had a full-sized sample at home I've used (2'x2' I got from a dealer). I also have the little mini-sample packs you get on Amazon, those aren't big enough to use though, cannot tell much. The thing I don't like about gray is the way it looks just sitting there when the projector is turned off.
You can probably still get the Elite sample pack online if you want to see the materials.
The SI 1.3 gain DIY material would be my pick. Dominic uses this, the only downside is it's always sold out and it's very fragile and easy to tear if you don't get it mounted correctly the first time.
We'll see though, things and taste might change after we've seen what the fabrics can yield of an image.
By SI you mean the Silver Ticket, yes?