Why choose one over the other? On paper, A50s seems to be the better choice but EL Amp 2 competes well if not better.
Element 2 is pretty solid, IMO at least it got some tuning (neutral sweet ish). Haven’t heard the A50S but it being the earlier models from Topping might mean their tuning is even less sophisticated than whatever it is now (A90, L30, A30 Pro - I think they are somewhat improving)