hi, I really have little to no experience with ball machine maintenance so tak eit with grain of salt. It appears that due to the very design the pneumatic machines (like older 'litle prince' or lobster models) are more defect-prone. They need to have the air tight seal to operate and it would seem leaks can occur in multiple places due to wear and tear. With wheels there's not much that can go wrong - as long as the motor is operating that's pretty much it. I'm also surprised that lobster machines claim to have faster ball speed vs. lower end wheel-based machines (like SAM models). I would expect wheel-based to be able to offer faster ball speed. Also, how does the ball wear itself affects the operation of either design? A well-worn ball will be just a tad smaller than a new one - wouldn't that affect the air tight seal that is needed to properly eject the ball in pneumatic machine. Opinions? anybody has experience with both types?