I don't usually listen to my Shures on small electronics or through a computer, but I can tell you that they are both, at 44 ohms, very efficient.
If you have a good music source, there is a significant difference between the two. If you primarily play low quality itune type files or run of the mill mp3's, then save money and get the 440.
For more check out this Shure brochure, especially the last page:
I will be using them with my computer i dont care about portability, and no i listen to flac