I’ve never ridden a fat bike in the snow. It looks pretty boring and slow to me. Lots of fat bike trails near me and nobody is wearing a helmet. Makes me think it’s too slow and non-technical to really worry about.
XC skiing is a better workout and probably translates better into riding fast. Just an observation I’ve seen from accomplished skiers and cyclists.
As for me, I put the skins on for the first time this year and had a 1500’ in 2 mile day. I’m struggling a little more with boot fit than I expected for brand new stuff, so I only did one lap. I’m currently shooting for 150k’ of uphill skiing this winter. Just for the fun of it.