We have Lone Star and Johnny and we love Lone Star. We are probably going to get buck at some point, but of the two, I would go with Lone Star, especially if you would rather have things a bit more firm.
I have both of these! And honestly, I wouldn't part with either one. My favorite part of Buck is the pronounced head, which you already have in Johnny... but my favorite part of Lone Star is the sheer "same thickness from top to bottom" intensity of it---so maybe I would tell you to pick Lone Star first so you're getting a different sensation from the toy you already have.