From my experience of buying and operating similar projectors for a camera club in the past I'd start out by saying the factors and figures you need to consider are not the ones they usually sell projectors on, and certainly applying bigger=better may not be appropriate...
Most projectors are not sold or built for displaying photos, video is often forgiving of a poor display.
Try not to listen to the herd too much. Around the time I was last purchasing the photographers who were highly respected on the club scene (PAGB affiliated bodies) made some very poor recommendations to other clubs who have since had to replace their equipment.
Light (lumens) output is a relatively useless number when you're looking at a device which is primarily going to be used in the dark, even a low output device in that price range will be beyond adequate in those conditions (the SX60 I've used has to be dialled back heavily to avoid blinding the audience.)
Again the assumption bigger is better does not apply when what you want is to express a range of tones in a darkened room. 500:1 is more than ample, bearing in mind you're probably only giving it 8bpc anyway so only have 256 tones per channel.
1900x1200 seems like the better bet on paper but the practical advantage is limited since if you want to use the full resolution then you are either giving a huge advantage to the display of landscape/letterbox images or limiting the output to the projection screen. The latter has the disadvantage that leaked light will be visible off the screen area and be very distracting in a competition/critique session (a lot may depend on your venue) and limiting relies on software support, which you won't have if it's garbage like FilmFreeProjection (which is unfortunately popular.)
So, what do I look for?
Ultimately you need to get the right type of display technology because that's what will determine the quality of your tonal range. LCOS is probably the best I've seen and after that LCD. Definitely avoid DLP since it has very little tonal range (and very vivid primaries).
Beyond that the proof of the pudding is in the eating and if you can find nearby clubs which have the projectors you're considering you may be able to get their owners to bring them over (or you could take a deposition and go visit them on a digital competition night.)