That's pretty circuitous! Southern Alberta, Saskatchewan and Manitoba are going to be pretty much the same thing as you'd find crossing the Dakotas. The biggest benefit I could see to you taking the northern route would be the opportunity to ride the north shore of Lake Superior and that may make the prairies worthwhile. Thunder Bay to Sault Ste. Marie Ontario (I grew up in Sault Ste. Marie) is one of the prettiest and most enjoyable motorcycle roads around and I highly recommend it. From Sault Ste. Marie you can catch the top end of I75 and run that right down into Ohio (bypassing Detroit via US23). That'll also give you the opportunity to ride the Mackinaw Bridge - 5 miles long, 4-lanes wide, with the center two lanes an open grate!

Gets a mite breezy too...

Never ridden a bike across it myself but I've driven it many times.
Oh, and gas prices will be higher up here too... They're calling for maybe $1.40/l ($5.32/gal

) over the summer - we-re currently between $1.10-$1.15 in my neck of the woods.
You might be better off heading over to Duluth and then around the top of Superior if you still wanted to do that stretch - a little more direct and you'd have U.S. gas prices for much longer.