AO Tennis has better gameplay for the mere fact that TWT is still broken (and will never be fixed), AO has the actual animations of the players ( which adds immersion) and there's a method and leaning curve to get good. TWT has a stronger BASE game, but it never had the chance to be refined. Now, if TWT gets a second chance, then i'd fully expect that to be the better series.
I agree 100%.. my main problem with AOT2 is the animations in general and the way the ball moves on the court.. maybe it's just my personal taste for this type of games but TWT feels better then it comes to this part.. everything else is better on AOT2.