I think that were we to ask Tolkien (and get an answer 😉 ), then I think he'd say that Tom was neither greater or lesser in power than Sauron, but not really equal either. If Sauron was on Tom's land, then I don't think he could do anything to Tom if he tried with all his power, but Tom couldn't do anything to Sauron, either. Tom's power has sway over his land and nothing else, but similarly, no power has sway over him in his land. That's why the Ring had no effect on him; it was a foreign power, and thus held no sway. And also, I don't think he has much (if any) power that he could use to fight Sauron, nor do I think he would use such power if he could. Nothing but his land concerns him, so Tom would probably treat Sauron as a guest. Outside his land, Tom has no power at all, and I'm not sure if he could even exist outside his land at all. So I don't think their powers are really all that comparable, because all power (in Tom's land) has no effect on Tom, so not even an army of Balrogs could probably hurt him. The problem with giving Tom the One Ring is that if Sauron walked up to him and asked for it, Tom would probably give it to him. He has no care for the events outside in that respect, and he would probably forget why he even had the Ring in the first place.
Well, that's my two cents. Thanks for listening to my rambling. 😄