The Duke was reviewed by ScottA (
link) whom I consider to be an expert on prostate toys. Based on his review, the Duke looks like a good choice for a hands free toy.
I do have the Billy and like it. While it is not a hands free toy, the benefit I like is that it can be manipulated, thrust, and angled by myself or a partner. The vibrations are quite strong.
I also have the Nexus G-Rider
link which I can also recommend as a hands free option. It has variety in vibration strength and patterns and for me targets the prostate well. I prefer to sit on this one and rock for maximum effect. Unfortunately, the bullet is not waterproof.
Consider also one of the Rocks Off products. I have the Cheeky Boy
link which I personally could not get to stay in without either holding it or sitting on it. However, it hit the prostate very well. The Rocks Off bullets are waterproof.
Both toys you selected are good. It will probably take some trial and error to learn what you like and what fits your anatomy best.