1. Given 2 SUV's, one a mid-size, one large. Both have +/- same safety features.

Is the large SUV always going to be safer given greater mass or, have current safety features tended to mitigate the mass effect?

I know the question requires some speculation.

2. Same givens as above.

Generally, the taller a vehicle the greater the risk for rollover. Is the rollover risk (apart from electronic stabilization) just a function of wheel base, curb weight and height?