My question would be
1)what type of space are you fishing in
2) how cold do you tend to get?
I fish out of an older Clam Jr. when I’m actually not hole hopping (maybe 10 times a year) and usually this happens when I can’t stand being home any more, and it’s subzero out. However the Coleman Catalytic heaters work just fine for me. In fact last January I was actually sweating and turned it off multiple times on one of the coldest days of the year, where the high was about -10.
I like them because they take up 0 room. for me thats a big plus I have enpugh other stuff with me that it can fit in the back pack, and I still can get everything else on the ice with me in 1 shot.
If you are not a fan of the cold, and 20 degrees seems to be heater worthy, and you have a little extra room to fit a little buddy heater I would say go for it. for me its just too much heat, and too much space.