The 10mm. They just seem as close to incandescent as you can get with an LED bulb. The extra 2mm probably doesn't make a ton of difference, but I like that the 10mm extend to almost exactly the same height as incandescent they are replacing. Basically, I'm looking for the best GI bulb. By best I mean that it looks similar to an incandescent in color and brightness.
For reference, I'm currently using them in The Shadow and The Lord of the Rings. For both I'm trying to maintain the classic yellow-ish (warm white) look of incandescents.
Please correct me if I'm wrong, but I think I've tried every SMD bulb that you (Comet) offers and I find them a tad too bright for GI, where as the 10mm Bullet Dome seems pretty dang close to an incandescent.