The 12 is 6 inches wider than the 10 and they say that makes a big difference. I was told that in certain circumstances the 10 could start a rolling motion in taxi that would not stop (or worsened) until the pilot slowed or stoped the glider and let it settle. At Howell airport (6/10 taxiway for smoothness) it was never that bad but there was only a 18 inch to 2 foot clearance on some taxi lights. A big roll at the wrong time and it might have been possible to get a light. Most thought I was being to cautious and it was almost impossible to hit a light if near the centerline while taxiing. This is no different than towing a pure glider down a taxiway with taxiway lighting I suppose except the trailing edge is exposed and damage is far more severe.

For what it's worth...