Whats the best product to remove urine from carpet.

I have tried almost everything...natures miracle, urine off, and most rug cleaners. Some work ok but the dog still goes back to the area to smell so it's not gone. What works best? Why?

Most products don't work that well but people buy them anyway, hoping that what they claim is true. It's not. The only ones that will do anything at all have enzymes, and the only one that I've found that actually digests all of the 5 components of urine is Pee-off. They also make a product for cats called Dumb Cat (same formula I think, but it also has a repellent)
Natures Miracle was not bad when it was first formulated, but it has changed dramatically and is basically useless...but it smells nice. Many contain isopropyl alcohol which dries very quickly...which is strange because enzymes need a moist environment or they quit working.
Either try pee-off (www.pee-off.com) or poop-off superior stain & odor, both have extremely high degree of safe bacteria (one bottle has about 3000 times the bacteria of all the leading brands)
Don't waste money on Urine off (its a copy but not a good one) or urine gone, which is a scam and there is even lawsuits over that brand.