The "best" is something of opinion and headphone model. The difference between the jds labs and arrow is not that great. I'd argue you have more options with the jds, because the boost is affected by the gain setting, so you effectively get 4 settings.
Here's the difference graphed.
The both roll back down, closer to 0db, at around 500hz and then very gently taper back to 0 at around 1000hz. So, basically they both impact mostly the sub bass region peaking around the 40-50hz areas. The c5 holds the bass at a fairly evenly boosted amount all the way down to 20hz or less. The arrow boosts mostly the 40/50hz area and drops back down below that.
But as you see with the c5/c5d, you get a few changes in the slope and shape of the boost based on the gain setting.
Either way though, they are both within a few db of each other and within the same basic frequency regions. The jds boost will sound a bit "fuller" if that's what you're after. I like it because it hits the super duper low sub bass area so you get that awesome round, full bass tone when you need it. mmmmmmmmm The arrow is good too though.
what software is used for these graphs?
You would have to ask JDS, as he graphed them. I'm not sure about the arrow graph...
On another note, I've finished my 2 part in depth c5 review if anyone is interested:
Edited by luisdent - 1/14/14 at 4:32pm