I just looked at these because of a thread about tubes in pedals and remembered Maxon has a few pedals with small tubes. What I realized is the vintage and the 9 series are super expensive and I rarely see them on pedalboards.
I have had the maxon tod-9 and most of their od's without tubes and the od-9+ I thought sounded the best of the bunch, the vop-9 had a nice boost going on too. Tubes don't necessarily mean better in od's.