Pro Carpet cleaning: Steam or Dry?

I’ve been happy with professional carpet cleaning services which use large truck mounted steam cleaners, like Stanley Steamer, but I wonder how that system compares with ChemDry and others of that kind.
The carpet is a fairly deep pile, medium gray with several kinds of stains.
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I never had a lot of sucess with the 3 times I tried the dry process. Despite their claims, the stains came back in the same spots less than a month later.
I now go with old reliable, and use the wet process.
When you wash your hands, do you do it on the front of your dry shirt with a handfull of sawdust (poor analogy), or do you use a wet rag and soap?
can't 'see' the orginal post so hope i'm not too off base here.from a dyi-er:did the dry a few times - imho- just not as good. if you got the $$$ a truck with nice hot water and a strong vacuum.i bought a bissell and use vinegar most the time as the soap, i find, is hard to get out. carpets look great.... every now and then - soap with the high traffic spots and spot remover for the, well, spots.
I just had a room done by Service Master. There weren't any bad stains, but there were a few rust spots under furniture feet. If you tell them when you schedule what the stains are they can bring the appropriate pretreatment.
The machine was a truck mouted four cylinder engine that produced hot water and high suction to spray and extract the cleaning solution. It took overnight to dry on a humid summer day, though I was in no hurry and didn't put the furniture back for a couple of days.
Thanks guys! I appreciate you taking the time to give me the low down. I'm stickin' with the big steam cleaner.