Flame Arrow better than Double Flame Arrow?

[ruisen2000]

I've always assumed that double Flame arrow was better than flame arrow, but when I looked at the dan ball wiki:

Flame arrow:
Creates five heat clouds per arrow.
With a bullets card 5, adding 6 bullets, there are 7 arrows x 5 clouds/arrow = 35 heat clouds.

Double FLame arrow:
Each arrow creates three heat clouds. Again, add in Bullets Card 5, 8 arrows x 3 heat clouds/arrow = 24 heat clouds, which is significantly less than Flame arrow, despite being its upgrade. Both arrows have the same damage, fire damage, and agi, though double flame has a larger MP requirement.

So... is there some hidden factor that I did not see (or arrows from bullets card 5 only causing 1 flame cloud/arrow?) Or does that mean I have to upgrade my sniper weapon again?

Edit: nevermind, apparently only double flame can equip a Bullet's.

[HueHuey]

Single projectile weapons don't accept bullet's cards