I haven't had experience with either of these units, but I have a friend with Don's preamp, and have heard nothing but praise from him. His experience paved my decision to buy Don's custom phono preamp, which I love,
I am however, on my second 6SN7-based tube preamp. My experience with both is that the tonal nature of these type preamps can be widely altered with tube choice. To a perhaps an even greater degree, selecting different input tubes changes the character as well. Have fun with either choice.
As to how tubey a unit sounds, I have found that the most tubey sounding preamps are tightly tied to coupling caps, and those more SS sounding work to minimize that or eliminate them entirely. My current unit is likely closer in sound to Don's. I love tube sound without any cap or transformer haze getting in the way.