The elephant in the room is Voldemort's instant kill spell. Somehow I don't think the ring would protect Sauron, seeing as it couldn't even protect his fingers from being cut off by a broken sword. On the flip side, Sauron can't be fully killed while the ring still exists. So that's where the debate lies in my opinion. Physically Sauron is far superior, but the magic in Harry Potter is seemingly far more varied and advanced. Not sure about a poll though, the last one only garnered a measly 11 votes.
Exactly. School students in HP are taught offensive spells. In LotR even a top dog as Gandalf the White couldn't sling a single spell to damage / hamper the invaders at the main door of Minas Tirith, and the duel between Gandalf and Saruman was similar to friendly duels between HP low level scholars. As far as i remember, the only real powerful magic we see in LotR is the surge of the river Anduin, and even that i don't recall if it was possible because Arwen was related to Maiar. Of course, Sauron is immortal and cannot be killed if not by the Ring's destruction... but so is Voldemort, as long as there are the Horcruxes
That's a good point, and Sauron effectively only has a single horcrux to Voldemort's seven. This reminds me of the time where I was debating Voldemort versus Sidious. (Sidious wins)