I went 15" Intel --> 16" Intel --> 14" M1 Pro.
I don't want to make this sound like I'm defending my choice so to be 100% honest about thing, at first, I did miss the screen real estate. It doesn't feel cramped or anything, but there is a noticeable difference. It doesn't actually hurt my productivity because I can comfortably edit two documents side by side and my needs are only occasionally more demanding than that. I am a heavy user of multiple desktops and Mission Control which really helps with that.
At home I just hook-up an external display and I use my MacBook almost 90% this way.
On the road, the difference is HUGE. The 15" Intel was close to perfect. The 16" Intel was only slightly bigger and heavier, but it was enough to make me HATE the thing when traveling. When I heard that the 16" M1 was another 0.5lbs I ordered the 14" machine.
It was the right compromise. It is smaller, but that makes me want to use it undocked at home as well as on the road. I have returned to couch computing and it's a quality of life improvement vs. being 'chained' to my desk. I never wanted to do that with the 16" Intel.
I checked out a new 16" in the store. The screen is spectacular, but the heft is real. It's quite the chunkster.
As for the thermals first ask what your needs are. If you're doing heavy video editing, or 3D rendering on the road and all the time, then sure the 16" has the edge. The 14" can carry similar workloads and might take a few seconds longer here and there, but it look a hell of a lot to get this thing to spin up it's fans. Everything else handles like butter.