I've had older, younger, and same-aged. I've found the most helpful thing has been their training and experience with my issues, as well as a willingness to try different (individualized) approaches. I can't work with a T who feels only certain approaches work with everyone, and those who do not benefit from said approach are not trying hard enough.

Age doesn't factor in to things for me. Current T is about 25 years older than me, but I'm not sure how much her age plays into it.