Coils

They always say that when you gain one thing you lose another or the other way around. If coils that have less ohms charge faster, than why not run 1.5 instead of 3.5? I'm just curious, I have to run a different coil. I found out that the coil I've been running is not the 3.5 that was on the box but 4.8. The reason why I ask is cause I have a 2.8 but don't know a lot about coils to know if that's a good idea or a bad idea.

Aaron