This is coming from someone whose tuberiding skills are suspect
but is a flawless tube really the best place to learn how to surf barrels well? Even I can occasionally point it and hold til exit but is that really skillful? What are you really learning? I'm thinking if you really want to learn to do this well, you'd want barrels that have warbles and random bowls/sections so you learn how to make adjustments in the barrel and get that exit, including those doggie door barrels.
I'd say most any relatively user-friendly well-shaped beachbreak with consistent non-dredging barrels would improve your skills at actually surfing in the barrel.