LT was great, but I think his legend has outgrown the actual player. It was often the case that LT could be handled for much of a game by a single quality offensive lineman. He'd pick his spots and make key plays, but the better OL could manage him on their own for most of a game. I've never seen a single offensive lineman contain Aaron Donald for more than a second or two, at best. Donald is almost always double-teamed and still has the highest pass rush win rate of any player in the league. Plus, interior pressure is almost always a bigger game wrecker than outside pressure.
And Aaron Donald is in tremendous physical shape and brings it all game long -- Taylor would sometimes show up to games drunk or hung over and was not known for having good training habits. We'll see what happens with the benefit of time, but I'd take AD over LT every time.