"Combat Swords is the fastest levelling spec"
that statment is generally true.
whats always true is combat swords is the highest DPS spec unless you have something like badge fists which greatly outclasses your current weapons at the time.
that said, combat lets you go in a fight from any angle, it lets you straight DPS, hit multiple targets, and emphasizes sustained DPS. for levelling i liked it up until about where your at now (62).
at endgame if your going to be PVE you want to be combat swords.
but at your level, you can go mutilate or shs. shs has some burst damage but is more cooldown dependent and will not perform well in raids. mutilate is nice for single target grinding which high burst damage and a lot of control, allowing you to keep a mob stunned for over half the fight, taking less damage, and ultimately more uptime.
its really a matter of choice for levelling as mut is very viable to use from 55-70.