I have a good friend that owns both, and it's Robowar for me by a decent margin. With TX the strategy is fairly simple, shoot lit spinner, hope to hit the target to advance a level, and when you're at 10 go for MB

With Robowar I think it's a more nuanced strategy. Advancing letters is great, and especially so when you've got the multiplier up to a decent level, so your shots are more varied.

On the music front, both are superb, but I think Robowar edges it for me.

I know about dropping the target banks (or hitting the lit advance level target) to move up levels. But by shooting into the pops (ideally via a lit spinner) you're getting pretty good points from the spinner, and also advancing two or three levels with some luck.

It's certainly the strategy that Keith Elwin suggests too in his pinball 101 video