And then you get guys who by an 1-1/2 tube wand, instead of getting a 2" straight through wand, which will decrease the air flow, but increase the water lift.
By 'increase the lift ' do you mean increase the vacuum rise time ? lift would also also be determined by what the motors can produce . Put a lift gauge on a machine with 2" plumbing and to the same machine with 1 1/2 .. no difference in ultimate lift imo .
I do not have a degree in quantum mechanics, but I have read up on the subject, water lift is exactly what is says, Its an old method of measuring, a pipe of a given size it attached to a vacuum, and its how far the vacuum can be lifted by the water. Now you can use a vacuum guage today. But I can guarantee you that of you have a 2" and 1-1/2" pipe its a physical impossibility to get more air through the 1-1/2 pipe than the 2" pipe, if you use the same parameters. And it also matters you hight above sea level.