"which pete smokes the best"
Well, that's a complicated question with a long answer, and the answer is going to be split into 2 categories. Peterson makes two totally different kinds of pipes, the "System" and "Regular" pipes. System pipes purposely make the smoke go through a very circuitous route in the pipe, and this condenses a lot of the water in the smoke. In theory, it makes for a gurgle free smoke because the pipe is designed with a place for the excess moisture to go. I have 3 system pipes, and they all have differently shaped tenon tips, and I've seen older Petes with different shapes again. It seems to make a difference - my 303 system smokes better than my 315, which is more bent and has a much "tighter" tip, and gurgled like hell until I modified it.
Non-system pipes are like any other pipe, and how well they work will depend on how well they are drilled, the size and shape of the stem (inside) etc. So a standard shape, like a 606 pot, for example, will function roughly like any other pot drilled that way. As a pipe maker, I drill pots with airways almost twice as wide as Peterson, so mine smoke quite a bit differently. But staying within Peterson, you'll find that all their small, straight pipes smoke about the same (I think the 31 is a straight system pipe, so it don't count). Pipes with a slight bend function very similarly to straight pipes, so things like a B10 are likely going to be drilled well and work well. I much more bent pipe like the 221 is more difficult to drill correctly, and in a sense, that's where the birth of the system pipe comes in. But if you have a non-system (like a harp) pipe, you have to hope that the tenon and the drilling in the stummel line up and don't interfere with one another. There's definitely no guarantee, as I highly doubt Peterson has anyone measuring tenons on each and every pipe. So a guy is hoping it was designed well in the first place and executed well at the factory.
Now, all that said, some people swear by system pipes, and others think that knocking moisture out of the smoke also knocks some flavor out, given that essences and oils are carried by the water which you are knocking out of the smoke with a system pipe. I'm not really going to offer an opinion that is anti-Peterson, because my system 303 is a fantastic pipe, but as a pipe maker, I strive for laminar flow in the airways and really try to limit how many obstacles the smoke has to clear before it hits the mouth.
What is NOT acceptable is a pipe that is sorta kinda in the middle - a pipe that condenses because of a tortuous airway and does not have a mechanism in place to deal with the moisture. That's a bad pipe.