A trailer is definitely easier to load/unload and you can take more "stuff" with you but with a good ramp/ramps one person can load/unload a bike from a truckbed. Pretty easily, actually. But I've had plenty of practice from hauling bikes around to trails, tracks, and bike shops over my 27 years of riding. It is kind of scary the first time you take your $10k baby up/down the ramp though.
If I could find a good deal on a 5x10 enclosed trailer, I would buy one but I only do 4-5 trackdays a year now so it's kind of hard to justify the expense.