I picked RK2, and here is why.
Essentially, if you like the rectifier sound over the mark sound, you will like the RK better. If you like the mark sound better then the rectifier sound, then you will like the mark V better.
But then that would just be a rectifier vs mark thing.
So I played it as the rectifier and Mark tones being equal but different.
That being the case, you are left with features and versatility. And in this case the RK2 is the clear winner.
I would personally tend to use the Mark slightly more though just based on my style.