Something else consider is that vintage scopes can generally handle the higher voltages encountered in tube gear. Also, you stand a chance of repairing them if the need should arise. More modern scopes are full of proprietary and specialty parts.
As for probes, I'd use HP, Tek, etc if I could afford them. Instead, I've just been using cheapo ones I got on ebay like
these. I doubt they really work well up to 100 MHZ, but are fine for lower frequency work.