The Infinity, for better or worse, is going to be the typical piezo UST. It all depends on whether you have a use for it. You can externally mix the signals of the M1A and the Infinity if you feel creative. It's really going to be a trade-off between the slightly electric tone of the M1A vs the occasional quack of the Infinity.
The Infinity can lead to other things, though, like if you want to try the Aura and its simulations.
Nick