I've done both, with Kodiak style tent and out of the truck bed with a topper. The topper deal was fine when I was in my 20's, now I much prefer a tent, you will be likely more comfortable in it. It will allow you more room... standing up, cooking / making meals,...
But the tent has some negatives also, cost, setup/ tear down, not fun with heavy heavy rain and run off water.
Depending on your truck and topper, you may be able have like an elevated sleep area using supported plywood/boards at about the top of the bed level and use the under area for storage of gear.
Good Luck,