why blue 100w bulbs are dimmer than 60w ones?
1) need to upgrade wiring and install relays.
2) they have blue coating on them - blocks much of the light and only lets blue light pass through! The clear glass 100w bulbs are very very bright.
Two things you need to be careful about:
1) your wiring - if it doesn't support 100w bulbs already then you may damage it if you dont upgrade wiring and install relays.
2) 100w bulbs produce double the heat - it could melt/deform the headlight's plastic housing in prolonged summer runs. Be careful about that.
btw, do mention which car you have in your first post.
And do let us know what you plan to do next and the results you come up with. Ideally get before and after pictures. You could do that by parking car approx 15ft from a plain wall at night and taking a picture of the wall with headlights on (low beam), then doing the same after getting the relay stuff done.
That way you could also compare the results yourself too and find out whether its worth the cost & effort 
