The NEC requires #6 for 50A service (55A max for #6 I believe), so you should stick with #6. For conduit I'm not so sure, 1" screams in my head but 40% fill is what I'd check against. 1/2" I'd imagine is too small, 3/4" would be close but still might be small.
Thanks for the reply.Ive been doing some research and 1"is a safe bet.I am going from my main panel up the wall to the attic and then out the wall to my sub panel.That will be the cleanest route.I will run #6 romex since it is in the attic.