The difference is the buckle belt goes on like a regular belt you use to hold your pants up. The lever belt has a lever similar to ski bindings that snap the belt to a set tightness with one pull. Each have their pros and cons. It's my opinion that a single prong belt is a good FIRST belt for most lifters. I've used both over the years.
The strength of the lever belt is that it is easy to get on and off without even breaking the belt in much. You adjust the placement of the lever with 2 screws on the inside of the belt. If you ever find the belt is fitting a little too snug or it's two loose, you pull out a coin, butter knife or screwdriver, back out the screws and adjust where the lever is placed. While it's not the end of the world to make an adjustment on the belt, it isn't ideal if you like a different tightness in your belt depending on what you're using it for. I might wear my belt tighter on the squat then I do on the deadlift, I might wear it tighter on bent over rows than I do on military presses...with a lever you're pretty much stuck with a single adjustment across the board or you're going to lose time making adjustments between exercises.
With a prong belt you won't have this problem. If you want it tighter, use the roller...looser, just don't pull it so tight. Biggest drawback is that the belt is going to be stiff as hell when you first get it and it takes awhile to break it in and get the hang of using the roller.
At the end of the day, both belts will give equal support. Neither belt is superior to the other, it's all a matter of preference.