Not sure really there'* no fair comparison. the SLE (which you see here) doesn't have the stability control like the Aurora does, and our SSEi has a rear end problem where it rides like a lumber truck below freezing so it bounces all over. If the SSEi didn't have the rear shock problem I think it might handle slightly better in the snow. The SSEi atleast has the stability control system.
I think they're almost identical in the snow though.
(best car I've personally driven in the snow was the 86-91 H-Body, second in line is the 92-99 H-body.)
The aurora is my favorite to drive in the snow though. If any clumps of snow, or just sticky snow flies into the windsheild while you're driving the windsheild wipers come on automatically to wipe the windsheild.
It'* nice to be able and keep your hands firmly planted on the steering wheel at all times. moisture-sensing windsheild wipers is something I don't think the Bonneville even were able to come with??