Sightseeing, comfort, or proximity? Both the Westin and Sheraton are decent European hotels (which means they'd be at least 5 stars in the US), but they're not near the center of old Munich; they're a short metro train ride away (or a bus ride, but I've never taken it). There's a Meridien in the center of town and it's a decent hotel too, but then you'd be spending some time going back and forth to the convention center. There are several lesser hotels (Four Points) - again, much better hotels in Europe than US, but they have no benefits except price vs the better properties for your stay.