The same dilemma today. It's freezing cold, 25-35 mph winds, making the windchill temp in the single digits. I think I'm riding the trainer.

The other day I rode my ALU bike, first time this winter. Boy, did I feel fast! My plan was to ride the steel bike all winter, but I decided, when the roads are clear, why not ride the better bike and climb some hills? I don't do much climbing in the winter because the sand and ice on the roads makes the descents too treacherous. The downhill was really sandy, but at least there was no ice, so I got down without issue. Getting up was even fun, mostly due to wind direction. It felt like I was being pushed from behind

So tomorrow, I need to decide whether to ride the steel bike or the ALU bike. I think I'm going to do steel, do just enough miles to meet my 100 mile/week goal. I'll save the ALU bike for nice weather hilly rides, and the trainer for unpleasant weather. How's that for a plan?