For MH, 70, 100, 150, 175, and 250 should be small while 320 and 400w are medium. For HPS, 50, 70, 100, and 150 should be small and 200, 250, and 400 should be medium. That's how it was done in the 70's (exept it was MV and HPS instead) all of this 400w in small fixture crap was all Westinghouse's fault, exept for the fact that MV and MH are tolitarable to those conditions, which HPS isn't.
I would tend to say ANYTHING over 175 watts should be in a medium fixture personally. 250 watt MH and MV are okay in a small fixture but are better in a medium. And yes that OVX needs a nice drop glass refractor, actually it needs not to be there at all!
I've seen that catalog dozens of times, last time I checked GE wasn't the only lighting company. It just makes sense to have 50-175 watts in a small fixture, 200-400 in a medium fixture and 700-1000 in a large fixture for all lamp types.
Yeah i know Ge wasn't the only company. It's the only one i have an old catalog on. I think the reason why 250w MV was in a small fixture was because 175w and 250w lamps are the same size, so it would affect the distribution of the light to use 250w MV in a medium reflector. I see what your saying though.