You may want to post this over on the Mississippi River Forum, as there are a few guys over there that fish the lake on a more regular basis.
Personally, I have neither specifically targeted nor accidently caught either species on the lakes. But again, I spend most of my time on the river and only occasionally venture on the lake in search of bass. I did see a 21″ walleye get caught off the pier by the vistor center last fall.
From the info I’ve gathered, Northerns on Lake Winona are few and far between and usually caught by accident……but the ones that do come out of there are usually large…….some very large .
The walleyes hang around the aerator’s and can be caught, although again, they are not incredibly prolific.
As far as which lake is better, I couldn’t tell ya……I would assume the big lake holds more of each species, simply because it is larger, although that does not necessarily make it any better.