I like my full harness,Black Magic.It is very comfortable and gives great back support.I can wear it without feeling "pinched"
I like going to different catamaran stores and see their inventory.You will find many choices online.Go for the more expense one as you will more than likely get what you pay for.
An old farmer that I hangout with sometimes told me more than once,
"Whatever hobbies you embrace,will cost you more than you expected.If you can't afford all the horns and whistle,you will not be happy."
My older Murray Marine half harnesses have that "Rainbow" color scheme across the back...not really a color scheme I want to wear...and they do "pinch" in a uncomfortable way

.They are OK for a thin girl to wear but not comfortable for the guys.
The long spreader bar is what I like for comfort and support.
If you wear a wet suit or dry suit with fleece undergarment ,you will need one sized to fit over everything.Buy one large effort to wear year round.
Good luck,Bill 404 21SE