I have five different bikes with four different shifters (actually five brands, but four types). I've never really learned to love grip shifters, but have them on my mountain bike. My OLD mountain bike, now a beater/commuter, has thumb shifters probably like your husband's (indexing, by the way, just means they click from gear to gear rather than being infinitely adjustable--it's a feature of the shifter, not a specific type). One of my older road bikes still has downtube shifters, levers sort of down by my calf, and my main road bike has "barcon" shifters, which mount in the ends of the handlebar. They have a lever to turn the indexing on and off; I leave it off.
I don't have a strong preference, but if I had to choose one, it would be the barcons.
Re the shifters hitting your hand, or vice versa, on most bikes the thumb shifters can be moved independently of the brake levers, so you can adjust them to suit you.