The real question is what does a monster's level mean? If a monster's level and a PCs level are equal measures of power then you end up with the 3e solution, where 4 PCs are supposed to fight 1 NPC of the same level. I guess that's ok, but it forces the GM to do a bunch of math whenever they have 3, 5 or 6 PCs, or when they want to do a more complicated battle. I prefer the 4e solution, where a Nth-level NPC is an appropriate challenge for a single Nth-level PC.
I don't think that solves anything. For one, "appropriate challenge" shouldn't be the same for all groups - some want more lethality than others - so it isn't as easy to define.
Additionally, you still need math in 4e, only the starting point has changed. Pathfinder replaced the 3e encounter tables with an "XP budget" system, similar to that of 4e, so monster level = character level doesn't in any way imply that encounter construction needs to be more difficult.
(Granted, PF also changed NPC CR = PC class level - 1, but that's mostly due to different wealth guidelines for NPCs and PCs. It shouldn't invalidate my argument.)