Certainly in my experience, a TVM queue versus a ticket window queue moves slower (I discount the odd occasion someone is buying a lot of tickets, or a travel card, which involves forms, photographs, and his Access won't wipe - you get the picture*) as people try and figure out how the TVM works. "Oh, go back Terry, you've selected Derby Road, not Derby; which one do we need to come back tomorrow? I've not got me readers on. Standard Open Return, or Off-Peak Return? Eeeeh, hang on, look at the Super-Off Peak? Are we returning on a day with a Y in it? Best look it up. Check the moon phases too, if it's waxing then I think we can get another fiver off. Right where does the money go? Bugger it's card only. Well I'm not putting it on the Visa. Go and ask the man, Terry. Bloody British Rail."
*kudos to whomever gets the reference there.