If you are concerned about ground clearance and will only use it occasionally, then you should probably go with the 3pt. hoe. Just be sure you get the heavy, top arm bracket. If you are going to use the hoe in a commercial venture, then you should go with the subframe.
When you use a hoe with a subframe you can lift the rear tires off the ground with the stabilizers. This makes for a solid setup and the hoe won't move the tractor around quite as much. A 3pt. hoe, in my experience, will not lift the rear tires, it just pushes up on the lower arms. This is not as stable as the frame setup. On the large hoes I have operated, they still were pushed around, it is the nature of the beast. A smaller tractor has a lot less weight to hold it in place.
I would suggest that you go with your gut feeling on this. You have talked with the dealers and GB and will have a feel about it. Sometimes your subconscious is screaming at you about things, the trick is learning to listen to it.