I level to balance the sound/response or it will sound ugly...but sure one amp or the other might not run as hard. That can depend on the efficiency and location of the driver as well as the power you run it with, of course lower frequency does take more power but the other factors do affect it. Even the amp can, I've had amps that will run a tweeter really hard and not make much bass before clipping, and amps that don't care what frequency it is once X gain is applied they puke. Not entirely sure why the amps work that way, but they sure do. In the latter case you need a much larger tweeter amp to work well. Maybe someone else here can shed some light on it. The amp that pukes at any frequency may have some limitation in the input section, as opposed to power limitations that can cause bass clipping.
Far as getting a larger amp, it may give more headroom or dynamics but I'll leave that to opinion. Personally I find some amps are more dynamic (not clipped) that others, so I don't really find any advantage to significantly oversized amps. Then I suppose with one amp you might need a larger one and another not. Another issue is just how much power is your system built for, if you use more efficient drivers you might not want huge/dynamic amps. Sure distortion can be harmful, but large dynamics can also overdrive a lower power speaker sooner. But if you like huge amps and set your gains right it can work great, all depends on what you want/like and what that install needs.