I've got a wall hangers at home, and have used sheffield stands at my old work, and on balance I'd go with wall hangers.
What I dislike about sheffields is that they scratch the paint on your frame, and your bike often ends up tangled up with the bike on the other side of the stand. Even with the recommended spacing, it doesn't leave a lot of room to get a bike with panniers in.
The downside of wall hangers is that you'll scrape your rear mudguard (if you have one), and you need to take panniers off before you can put the bike on the rack, so make sure there's somewhere that you can lean a bike whilst you sort out panniers.
I've found that hydro brakes can go a bit spongey after being hung, but it always comes back after a few pumps. I've always put this down to the seals retracting a little bit as the fluid is pulling them back under gravity.
Whatever you go for, make sure that they're generous with the spacing. Trying to squeeze more racks in is a false economy if you end up with some spaces being unusable.