I haven't actually ever tested these in a custom game, but I assume they change the field of view for everyone. I personally prefer the wider field of view, but I don't really feel comfortable changing it for my maps, since it would cause the game to feel different than what people are used to. Plus, you can't combine it with other filters. If you're not sure how field of view impacts what players see, you can check out the first few posts in this thread - http://www.forgehub.com/threads/halo-science-thread.147778/
One major drawback is that aim zoom will not work if the filter is set, rendering it practically useless in any serious sense. Been a while since I tried it though, might be fixed now.