Right. Your forum stats show you are a ninja. DPS queues tends to be the longest, so your times would often be improved if you had a healer or tank friend along for the ride. You can try your server's novice network, among other places, to find such people. Also, on many servers, language selection can make a big difference. So consider your willingness to use auto-translate to talk to people and mark additional languages for yourself.

To directly answer your question, though, Level 60 will probably be a bit faster since many people are just passing through Level 50 stuff relatively briefly but more are staying at Level 60 stuff much longer.