I love PJ's vision for LOTR, and I agree that The Hobbit, no matter who does it (even if it's PJ) will be held up against LOTR. The fact is, just based on the differences in books, I think public perception will be that The Hobbit is a lesser work, which it is.
I don't think anyone in either camp should feel hard-done-by though. Whatever happens to The Hobbit, it'll never change the fact that together they all made three amazing films that work seemlessly together to become one superb adaptation of one of the greatest books ever written. Next to that accomplishment, The Hobbit could never be on equal ground.
I'd love to spend more time in PJ's Middle Earth. Even at four hours a film, I feel like there's more. And maybe that is for the best. I sort of feel doing The Hobbit might damage the magic of the trilogy, much as the prequels have stained the OT. I'd hate to see that happen.