From my personal experience I like the 30s better...but there is a lot of bias for me on the 30. I've had 30s ranging from an 1800fom up to a 2000+fom and I had the UNS LR A2 (new 30) and a white 30 so I have a lot of hours on that platform.
I have never mounted the 27 on a rifle and shot with it so that basically makes my opinion worthless from an actual user. It did have a great image and the focus knob in the back was neat, I just don't have enough time to say I like it better or worse.
Since I have a clipon with a white tube this just sits in the safe to keep it as nice as possible for a future retube donor. After a recent move though I kind of want to try to a pvs24/uns-sr to see what the world of small clipons is like.