PSN is finicky. Don't worry too much about it. You'll drive yourself nuts. Do what you can on your end (network settings, etc), but don't go crazy.
I get slow store and patch downloads and slow trophy syncs, but gameplay is unaffected (since it doesn't rely on Sony's network). However, I get speed readings on my PS3 comparable to my PC and 360 (~5Mbps). So it may actually be an issue with your home network or ISP if you're getting a different reading between different devices.
PSN & XBL ID: drop me a private message