Not sure there is even a 5/3. Maybe you meant 5/4/3? And that's what I rock.
Not sure how long you been surfing, but wetsuit technology has gotten insanely good. The new 5/4/3's feel like 3 mils compared to those cardboard 5/4/3's O’Neil used to make.
In my opinion Xcel makes the bomb. If you want one suit for all year round, get you some. Otherwise bathe in your manliness