You can get away without a resistor use a motorcycle flasher relay for LED's.
There is no direct comparison between LED and a "normal" bulb ,as one(bulb) is tated in power consumed whereas the MCD rating is output in CANDELLA, and advances in LED technology, particularly by CREE, mean a modern LED can put a shed load of light out for next to no power.
I have some FENIX torches, from glowgadgets.co.uk, and the small P1d CE is 130Lumens, the P3 D Q5 I have is 200 lumens takes 2 x CR123 batteries, but is BRIGHTER than a FIVE D CELL MAGLIGHT, despite being, around 1/2" in diametre and about 5" long!!
If you want me to find out comparison of candella/lumens etc I can ?
tabetha