At 27 I would defo have gone for the 37 year old.
Now however (I am 40 ish), I am a dirty old woman, and would choose 20 but just can't find any. In the last 5 years though I have been out with many in their 20's and early 30's.
Just choose the one you fancy the most.
Younger - DEFFO!! My fella is younger after always seeing older blokes and he is much better in bed than any of them!!! Toy boys are the way forward!!!!
the 20 year old would have the youth and innocence and the 37 year old will have the experience and no doubt a generous lover. If you want marriage and kids go for the older one, more likely to make a commitment cos he's closer to the grave.
Don't want to boast (well not too much) but as I have got older, the younger ladies seem more 'friendly' towards me without much effort on my part....lol
I think its down to confidence and sense of humour in my experience.
def older - i'm 22 and my boyf is 35 - and its just works. but i guess it depends what kinda people you are...whatever (whoever!) works for you...Never been with anyone younger or same age as myself...