The EMP speakers are more in the league of the Infinity Primus speakers. I couldn't tell you which one is better. If I had to choose I would pick the Infinity speakers, because of a more solid cabinet, deeper bass extension, and their renowned drivers. I haven't heard the EMP speakers, but I have some Infinity Primus, and I know they are great speakers. I watched Kingdom of Heaven today in my home theater with the Infinity speakers, and I was able to really blast it (which I don't often get a chance to do), and I was blown away by how good the female vocals on the music soundtrack sounded, just gorgeous. Crystal clear, even at -5 on the volume dial on my Onkyo. An absolute steal for what I bought them for, $130 each. I think they would still be a great bargain at $300 each.
I think either would be good, miles ahead of the Aperions in any case. If you are not going to use a subwoofer, I would go with the Infinity speakers, as it looks like the EMPs are going to be pretty weak on the bottom end; just compare the frequency response specs, 50Hz-20kHz ±3dB vs (±3dB): 38Hz - 20kHz. I think that's why EMP is coming out with the E55ti speakers soon, to have some towers with better bass and also to bring up the tweeters to a more common ear level. To be honest, the E55Ti look more comparable to the Infinity Primus p362 than the E5ti, at least in performance specs. But this is all just the 'tale of the tape', to use a boxing term, the right one is the one that sounds best to your ears.