Many factors to consider in deciding when:
Availability of my time- If it's a work day, I'll have to clear it in the few hours between getting home from work and catching some sleep. If, like earlier this week-and rarely- work is shut down due to very heavy snow, I'm likely to clear several times during the storm.
Availability of equipment- Two years ago, I loaned my walk-behind snowblower to my son. We got buried with about 24" overnight, so I had little choice but to use the 755 with FEL, because I thought that was a bit too much to plow with the Gator.
Predicted or actual weather conditions- If it's snow that will change to rain, and I expect to be able to clean it up before a hard freeze, I will wait until the rain stops. I'd rather clean up snow with an icy glaze than clean up the snow to allow the icy glaze to form on the (almost) bare ground.
In general, for 6-8" or less of snow, I plow with the Gator. Larger amounts, I prefer the walk-behind snowblower, for the exercise and because it doesn't create massive snow piles. Last summer, we purchased a 4WD Ford Ranger for SWMBO. It came with a snowplow, so that's a 4th weapon in my arsenal. I actually ended up cleaning the 3 driveways with the snowblower twice, then finishing up with the Ranger by scraping clean with the blade while i a comfy warm cab.