Let's quick compare a from-scratch NPC per the DMG rules (pp.187-8) with a Monster with a Class Template (pp.182-3)...
Both have essentially the same powers, proficiencies, skills, and features and the same mods to defenses (or, at least, I didn't notice any differences).
NPC has Second Wind (albeit with only 1/2/3 Healing Surges per day), so essentially 1.25xHP (with a cost of a Standard Action to get there).
Monster with Class Template has +2 Saves, 2xHP, and 1 AP. All three of those are VERY significant effects to enhance survival in combat.
We know the Monster with a Class Template is an Elite.
From that, I'd argue the NPC built as the DMG suggests is a standard (if a bit on the beefy side) monster of his level, because he'd be shy several very significant abilities of the Elite.
Now, a fully-built PC style NPC... Well, that'd be a bad idea, IMO. Too many powers for the DM to manage effectively, specific Feats to be picked and managed in play, several Healing Surges an NPC will likely never get a short rest to be able to use, and little else. Not really a significant step over the DMG rules NPC except in bother.