I have used a quad/atv for ice fishing for a few years now. Allows me to access lakes not accessible by vehicle and before ice thickness is safe for vehicular travel.
Over the years I have changed a few things in my arsenal to make using the quad even more convenient (rod case, rear cargo box, auger mounting).
I concur with the previous posters Honda recommendation. Would add for improved ride quality, especially for the wife on back, independent rear suspension be worthwhile. I run a Suzuki King Quad personally as I prefer cvt versus Honda manual. For reliability my vote be Honda, Suzuki and Yamaha.
Here is my current set up, Suzuki Kind Quad 750 with power steering. Rear box is an Otter Monster box which my Otter rod case attaches to the side via a slide mount and on other side I have a milk crate with the same style mount to haul my Vexilar or propane bottle in. Inside monster box I can carry my lunch bag, tackle bag, ammo box power supply, underwater camera, Vexilar or 5lb propane tank, extra gloves etc. ice auger is carried on front rack via Rhino mounts. Quick note also that if pulling a sled/toboggan behind a quad/snowmobile you must use a solid hitch(no tieing it on with rope only).