Light seems actually worse for button-mashing IME, since you have to keep party buffs up while you dps with your ki strikes. For dark, most of the finishers except for touch of despair are inconsequential (though void-dark-void can be fun sometimes), and the main moves you'll be using all the time are unbalancing strike (to proc your sneak attacks!), stunning fist, QP and sunder. Even the one finisher you'll probably like to keep using all the time can be easily prepared through opening with shadow fade, dark ki strike and touch of death.
Originally Posted by Beer_Dude
On my helf 2nd life dark monk, I went cleric dilly for leveling. Self-sufficiency seems a lot better, as you'll have more heal amp for being helf. Once you cap, if you find yourself not needing the scrolls due to SF pots (and monks are especially good at using sf pots due to expanded movement speed and abundant step), you can switch to rogue dilly and easily outpace the half-orc in raw sneaky DPS.
The real reasons to go light in my opinion are Kukan-do, Jade Strike (dropping fortification = win) and DR breaking (which isn't as big a deal as it used to be since devils went a bit out of fashion)