I do both trips every other year or so. Up to Ontario for big smallies and down South for big large mouths. The correct answer is.............BOTH!!!! Bass fishing in great water is awesome regardless the species. The thing about smallie fishing up North is that you can usually go out on almost any day and catch 20+ fish. You're really not having a great day till you get to 40. Never really seems like that when fishing largemouth. 20-30 is a pretty awesome day largemouth fishing usually. And, up North, there's just NO pressure. It's so much easier to catch em. that's been my experience. I love em both though.

Meh......

those are huge

Hardest fighting smallies I've caught came from the main tributaries to the Columbia River out in Oregon. Of course, the current your running your bass boat in is sometimes so strong that you are quickly being carried downstream unless you get on plane. Running a bass boat through riffles is a thrill in itself. Just make sure someone else does it first (or go with a jet)! It feels like those fish are half salmon when they hit the current. Other good thing, there are tons of them! Smallmouth are invasive species out there and a lot of Oregon residences would rather see you throw them on the bank. Fun fishing for sure! The football smallies up north are still a blast, but they don't even compare in fight to a true river smallie! One of my buds is now guiding in Oregon . His name is Larry Cross.
http://www.willamettevalleybass.com/#!about
This guys is a master at smallies, but he will put you on good largemouth fishing too.

The perfect time for you guys to do this is end of june or beg of july when its hot down there. You can go to northern MN or WI and it will be 70-80 degrees. On a bad day you can catch 20 and on a good day 75-100.