Riddle me this... (Ping)

For a while I've been playing on my alt, in preparations for getting him ranked too before the season ends, but here's what's striking me as odd...

My main account plays at a consistent 10-11 ping. My alt plays plays at a consistent 17-18 ping.

While they are little numbers and for most players -already- pretty high speeds, there is one thing very, very odd:

Why am I getting two different internet speeds while playing from the SAME computer, on the SAME network route and provider, on the SAME league server? Those numbers should be similair. Why aren't they?