A mexican backroll is where the rotation is initiated by tucking your head towards your knees causing a more 'rail over rail' flip than the traditional 'tip over tail' flip initiated by looking over your lead shoulder.
I don't have an answer for you in terms of 'easiness'. I will say that the mexican is the precursor to learning several more complex inverts, while the 'regular' backroll is usually the classical backroll people learn first.