[decipha]

nothing,

no one tuner is better than any other tuner

'tunes' as well, knowledge is key

in order to properly tune an engine you need to know whats going on with it and where you want it to be, then you need to figure out how to get it to do what you want it to, thats it end of story

the first thing done when tuning an engine is having an idea of how you want it to perform

if it doesn't perform the way you expect it to then you need to investigate

[cgrey8]

When you say "tuner" are you referring to the hardware/software tools or the person? There's plenty to be said either way and the answer is almost never "nothing".