I raced in Mike Lasher's car last week with his Simpson Belts and they were awesome. They have sewn in handles ont he shoulders that work nice for hanging on to. I believe you can also request to have them be a pull up style on the lap which makes it much nicer when tightening the belts.
I currently run the PRP harnesses in the Fatrod and they have been the most comfortable harnesses I have ever ran. They have a smooth almost gel like padding.
In th enew RZR4 we just put in the new BEARD padded harnesses which fell almost identical to the PRP's. They are super comfy and what i like about the BEARDS is they have a sternum strap that is adjustable.
In Magnum Dan's Milk Truck Rhino he had CROW's which were awesome as well, you cant ever go wrong with CROW products. They also had a sternum strap but they were not adjustable which was kind of a pain.
I would consider the BEARD and PRP products if your looking for something really comfortable and or the Simpson product if you want something more race inspired while retaining the comfort side of things. As most have mentioned with any harness unless you are racing I would request sewn in padding.