Which better for relationship and why

Depends on what kind of "relationship" you're looking for.

I need an inny (woman) myself, don't see two outies making it work.

There shouldn't be much difference if they had gender affirming surgeries.
Biggest difference would be how you think & feel about it all. Can you get over the fact they were born as a male and lived as such for a long time?
Men who had sex with a trans woman say they didn't notice a difference.
But I suspect many men have an ego problem with it.

Personally, me being a woman, I find it a bit weird in the sense of, what the hell do they know about being a woman? They never had a cycle, don't know what it is to have a period, grow breasts naturally as a teen, to be pregnant and feel your baby movie inside your womb. That beautiful sensation when you breastfeed and the milk moves, what it's like to become menopausal, and so on and so forth.
They've been made a woman by surgeons' hands but on various levels they have never experienced what it's like to actually be a woman.