Using this instead of the +7 you can replace some of  your +hit with +crit and thus boost your damage way beyond +7.

Also, at some fights you have to use resistance gear, and they generally don't have +hit, so you'll end up missing alot.

It's especially useful on the Huhuran fight where you're required to have a lot of NR gear to soak damage while using tranqulizing shot. A few misses there can mean a wipe, since she does quite a lot of damage when enranged.