Floor for early season (Aug/Sept). Bugs just annoy me, whether ants all over the place, mosquitos (not often), bees or regular house flies landing on me during the mid day nap. In Oct either is fine. It's not too cold or wet, no bugs, etc. Nov, Dec...either is fine as long as you have a good sleeping bag. In my zero degree bag I can sleep through anything. While I haven't used a stove in late season, I could see the benefits for drying out your boots. Little warmth is great, but not a big deal. Frozen solid boots (from sweat or snow melting) kind of suck the first half hour of the morning.
Tarps are half the weight, but that's a difference of a 1 - 2lbs compared to light weight tents. Tarps can be placed in much smaller areas or on crappy terrain, where a tent requires more space. I also like bivy's once it gets colder. I can sleep anywhere. I climbed up a mountain once and decided to spend the night rather than hike down. I couldn't find a decent place to camp without feeling like I was sleeping where the elk might show up at sunrise. Ended up sleeping in a deer bed perched under a mini cliff. Just enough room. Not the greatest nights sleep due to wind and elk bugling at 4am, but I woke up to elk 300 yard below me and above me. Kind of surreal experience.