HTC Desire, HTC Evo or samsung Epic 4G?

So I am thinking of getting a new android phone, am looking for a quick processor and large RAM because I hope to use some applications based on OpenCV library (I think I will need a lot of RAM). I have never developed anything for phones so correct me if I am wrong.
three phones mentioned above have 1GHz processor, but it seems EVo has 440MB Ram, Epic 461MB and Desire only 123MB !!! which is really surprising. How come desire has so little amount of RAM? Does it mean running parallel applications on desire is slow? have they compensate for it in another way? Also I have heard that eventhough the clock rate for all processors is 1GHz, samsung's technology has made the processor run faster (more efficient), would you say so based on your own experience?
Final question, I will be getting the phone end of October, do you know if any new phone will come out by then? (UK market of course)

Thanks a lot