Probably fucked either way. The bear would be painful, but the spiders might give you a chance if you don't bother them and stand perfectly still for an hour. But if you still get bit, you can die in that painful and prolonged way. You could probably try to smash the black widows too, if you want to go out as a mass murderer of spiders, rather than go out as a knob killed by a bear in one swipe.

Apparently if you do not run or act aggressively towards a grizzly bear, or even try to play dead by keeping still and calm, it probably won't attack you. Contrary to popular belief, bears don't eat people either. However as Box points out, with the spiders it would only take one or two of those million to bite you and you might suffer a painful, slow death. So I'll choose the bear. And try not to panic. Much.

Either way, the answer is NOPE NOPE NOPE NOPE. Well, OK... if I had to choose, I think I would go with the grizzly bear. Maybe I could try to quietly hum or sing a lullaby, and just pray that it would keep the bear calm. With the spiders, you'd just be completely at their mercy, and if you smelled funny to them or bugged them (ha ha) in any way at all, they could easily bite you and kill you.

By the way, I have always thought the music from Chopping Mall would work really well in a movie about killer spiders.

I'm going with Fuad's answer.

Depends how big or small the room is. I know black widows are very small compared to us but one million is an awful lot. Spread all over the room no chance in hell I would survive that. So yeah the bear it is.