Most anglers will use a piece of a nightcrawler or a half nightcrawler when fishing for perch. If you get on a school of big perch though, they may want a full nightcrawler. Walleye anglers catch a lot of their biggest perch when fishing with a spinner rig and a full nightcrawler, so it could be a good way to target some of the bigger perch. To put more fish in the boat though, you will almost always do a little better by using a piece of a worm or half nightcrawler.
Red worms are the perfect size bait for yellow perch. The full nightcrawlers work well too, but if you can find some red worms, they will actually work better for most of the perch you are going to catch. If you are looking to target some of those jumbo perch, you may want to go with the fatter nightcrawlers, but plenty of jumbo perch are caught with red worms too.