The 918 will be brilliant indoors but even the 618 can have a blinding affect on the user. Anytime your eyes have become accustomed to darkness the affects from these high intensity lights will have a negative affect on you as well BUT, the good thing is you know what's coming and you're behind the light. Now, if you don't mind spending a bit more you can add the difuser covers (Beamshaper) which will lessen the intensity and helps broaden the flood a bit.
618FA will be good on out to approx. 50 yds. depending upon conditions while the 918FA will cover out to 80+ yds. if conditions are optimal.