Depends.
We fished Cass for 3 years in a row in the fall-mid to end of October. We had only a few good days on the water. Other days were too cold & windy or the fish just shut off. If the conditions are right, Cass is incredible. Lots of 16-18″ fish and a real good shot at a 30″. But it is big water and can be VERY cold (not much different than Rainy I suppose). We spent most of our time vertical jigging and took fish from 20′ to 60′ of water on steep breaks. Nice lake, very clean, somewhat clear-lots of structure and not much traffic. About 3/4 of the lake shore is reservation and completely undeveloped. Pike bay(I would guess 3000 acres by itself?) is attached and accessible by water and offers a better chance for a trophy.
Also-within 15 minutes of Leech, Winnie or Bemidji if Cass is a complete bust. I have a friend w/ a camper at Stony Point Resort. He is there at least once a month-esp in the fall. I can give you some spots to target w/ some notice if you decide to give it a try.