Johnbender,
It has been a while since I moved from the P25 to the VPI Scout. I find it hard to discribe a difference in sound.
I use a Lyra Dorian in my Scout. The Scout is a bit smoother less in your face then the Rega I think. Rgea is more about attack, fast en detailed. The scout to my ears is more about music. When I'm shopping for new gear I never go for the warm sounding, or the in your face sounding gear. I want to hear the details as part of the music. I don't want to listen to independent sounds. Neither do I want an overly warm and lush sound.
When I hear an acoustic gitaar I want to hear the small sound (ting) when the player hits snare but only as part of music the instrument makes.
I think I get that from my Scout with Dorian, the scout has a good foundation, the Dorian takes the music out and let me hear it.
I hope this was of any help.