in my opinion a well built saff is better than ahmose. two reasons for that to make me come to this conclusion:
ahmoses biggest cryptonite is magic and stuns. ahmoses skill also got nerfed a while back. so since then i think saff is better, especially in HR since most bosses are either magic or have magic minions. at the end you should pick the one with the highest defense stats and most HP, however some heroes seem to gain medals better than others and saffs cards for sancts cost only 500 each. so you should continue to develop both and only stop when you can say "ok this hero is awesome now" and then focus on that one.