Right, but the number of die rolls performed by the DM and the players (total) is pretty much the same. Sometimes there's an equal number of enemies. Sometimes there's one nemy with a number of attacks. But the probability of one of the players critting or whatever and the DM doing it with one of the enemies is pretty much equal (barring "builds" made for crits, etc..)
But a key difference is always the emotional investment. Most players are invested in their characters, and very often, even the DM cares about the individual PCs (because he might have plot-hooks for them to draw them into the next adventure, or just because he enjoys seeing them in action) and the party as a whole.
The emotional investment in most NPCs and monsters is pretty low. They are exchangeable, and aside from maybe a few recurring NPCs (allies, nemesis, family members of the PCs), you care little about them. And if the few ones that you care about are killed by some lucky roll, the scene usually is anti-climatic.
Like those "Scry-Buff-Teleport" encounters, or at least the "buff up before facing the BBEG" - the party is optimizing all its defenses, casting every buff spell at its disposal, uses potions, and gets to the BBEG (either by Teleport or just traveling the remaining distance) - and the first action of the PCs just kills him. Like a succesful Save or Die attack. All the suspense was build up in planning the encounter, but the pay-off is a 1-round fight with the BBEG being totally ineffective?
---
What I noticed about the above: The buffing part of 3E got easily out-of-hand and often created statistical nightmares - but it definitely helped building up suspense. The party looks at everything they know about the foe they are about to attack, and tries to optimize its spell selection, buff distribution and work out the battle tactic (usually which short-term buffs to cast, when to cast certain attack spells, which foes to engage first, and so on).
Maybe that will be something I'll miss in 4E. The entire buff selection part is gone. (But the up-side is - the buff recalculations are gone, too. And those really bogged down this type of encounters.)