With the patch looming, a guildie of mine suggested that he might try out Smitelol for its DPS. And with the new Penance glyph and the buff to Penance damage, I was curious what the numbers would look like. So I went over to the test realm to give it a try and do some comparisons.
I tested three different specs-- a Shadow spec, a Smitelol spec, and a Penancelol (51/20) spec. I'm not putting specific specs because they're intuitive. In all cases I used the same gear set, which is a bit heavy on crit and relatively spirit-light. In all cases I had a Flask of the Frost Wyrm. My opponent was the Masterwork Training Dummy (level 80), not the heroic dummy (boss) because the specs have different hit requirements and I wanted to keep the playing field relatively even.
SHADOW: was pulling 2700-2800 DPS. I'll admit my use of shadow is still a bit primitive; I didn't have a very good feel for when to use SW: Death, so I just hit it every now and then. But I kept DoTs up and Mind Blast on cooldown, so I think I was doing it right. Mana wasn't really an issue.
Smitelol: 1850 DPS without PI, about 2k with. Mana was a huge issue. I used PI off the bat, and my intent was to use the second one at the same time as Shadowfiend to give shadowfiend the haste buff. It didn't work. I was forced to Fiend before the PI cooldown was up (!) and then potion to keep nuking through the duration of PI (!!). Note that this was in relatively crit-high but spirit-poor gear. I got relatively more SoL procs but my regen was not as good and so my endurance may not be representative. Spirit, not crit, continues to be the key stat for this IMO.
Penancelol: 1750-ish DPS without PI. Probably would have been in the 1900 range with. My gear is probably bad for this build, which really has no benefits from crit; it needs straight spellpower to succeed. Anyway, overall it's just a healing build with a couple of nuking talents.
CONCLUSION: Shadow >>>>> all for DPS. Smitelol is fun, but ultimately nothing more than a leveling build. If you want to nuke, it's shadow or nothing. Penancelol was surprisingly competitive with Smitelol, but both of them are just toy builds-- sub-optimal healing builds with modest nuking capacity.