Or you can compare an Orc to...anything that's CR 1/2. Hell, it beats plenty of CR 1 mobs.

At CR 1, spider swarms will utterly kill almost any other CR 1 mob head to head, and a party without blasty magic is pretty much screwed against one at level 1. Even with a caster, it could get ugly. Especially if it's say, at night, and thus, the caster can't see them till they attack.

On the other hand, a Giant bee is CR 1, and will actually kill itself trying to take out a single player of any type, even at level 1. It's also not aggressive, so this will only happen if the player actually attacks it and fails to kill it. So, these things are pretty much slow moving piles of xp.

CR is only a guideline at best.