Are you planning on using the amp to drive the VR Jr's or some other speaker? This will be a big determinant of what result you'll get.
The 300b amps in general are lower power and will need a very efficient speakers to sound their best. They tend towards glorious midrange and rolled off low & high frequencies. Tubes are some of the priciest.
EL34s lean towards a balance that's great w/rock, warm mid-bass, and great rhythmic drive. Great ability to tube-roll to tailor the sound.
Although not as familiar w/your model, my old VRs preferred amps with relatively high current vs. other tubes designs(e.g. BAT).
More info will help...Cheers,
Spencer