Hey Flash,
The answer is 'do what floats your boat'.
Slow or fast doesn't matter.
Maybe you need a weight training specific winter program? Cross training activity for the cold days? Fat bike? When I lose 10 pounds, it's soooo much easier to go fast!
You'll face a similar decision, several times down the road. It's the old risk/reward trade-off of staying physically active outdoors. You X-country ski? Great exercise.
ps - i grew up in Nashtown, not far from Vandy Stadium.
__________________
Vintage, modern, e-road. It is a big cycling universe.