Depends on what lighting you have. Brighter light will allow you to use slower (finer grained) film.
Faster film allows you faster shutter speeds. This could be important if you need to freeze action in low light.
Let's lay out a fictional scenario for example. Please bear in mind I'm making this up, so nobody howl if the numbers are off.
Let's say you're shooting indoors in weak light. You're using f8, because that's the sweet spot for your lens. And you want to freeze the action. So....
using asa100 your shutter speed might be, say... 1/15 sec
asa200 - 1/30 sec
asa400 - 1/60 sec
asa800 - 1/125 sec
asa1600 - 1/500 sec
Okay, obviously anything below 1/125 sec probably isn't going to freeze much movement. So in this make-believe world I've created you'd have to use at least asa800 film to freeze action.
Now there are several things that can mess up my scenario:
- using flash
- newer auto-everything camera/lens that has stepless apertures
- 17 things I can't think of at the moment.
But you get the general idea. The tradeoff for gaining a faster shutter speed is grain. The faster the film, the more noticeable the grain. You have to decide whether the tradeoff is worth it, or if you can use a larger aperture, or flash, or...
I'd go get some 100, 200, & 400 and shoot a roll of each to see what best meets your needs. You might like the "grittiness" the 800 gives you. Try 'em all & use what best suits your objectives & your critical eye for a finished product.
Now wasn't all
that just clear as mud?
