depends on what you expect to encounter.

A long wheel base with 26" wheels will bottom out when going over snow banks.
I smacked my long cage derailleur a few times with my CX bike over some small snow banks.

if you're just riding on pavement and want your tyres to sink into the snow and touch the pavement, then adding extra weight to narrow tyres does a lot. With an extracycle I'm sure you can load up the rear for extra traction.

if you're going off road and want to float on the snow, then having fat tyres with a normal wheelbase helps.