Tons of threads on sumps and their advantages. I suspect there are plenty of folks who are completely successful with canisters as well, but personally, I know numerous people who moved from canisters to sumps...and exactly one who went the opposite direction. He did that strictly because of space limitations on the display tank in question, and continued to use sumps on all his other tanks. I haven't owned a canister in many years and don't see myself ever buying or using another.
So I'm obviously going to recommend you go with a sump. But, even if you don't...you do, after all, already have those canisters...you might consider getting the tank drilled when it's built, and then simply installing bulkheads and sealing them off with threaded caps. You can always upgrade (and it is indeed an upgrade!)
to a sump at a later point by removing the caps and adding the plumbing.