there is a lot of talk abt the differences between software and hardware compression, reverb, delay, eq or whatever, but is there any difference
between hardware autotune and the plugins???

plus, is there anything better for pitch correction than autotune (when used in the graphic mode) ???

A good vocal performance rarely means constant perfect pitch. The graphic-mode of the plug-in allows spot correction of not only the offending note, but sometimes just a portion of the offending note - leaving the nuances of the performance intact such as glissandos, grace-notes etc. Many times I will leave the performance alone except for long-held notes or during vocal harmonies where it can really make things blend beautifully.
The hardware version is much less forgiving. It is designed so that anything outside the set threshold will be corrected to the set amount within the set scale.
It would be nearly impossible to make all these settings tight enough to correct any glaring mistakes, yet loose enough to keep the nuances and vocalists style sounding natural. On the other hand - for a live performance in a noisy environment the newer models can typically take care of the ususal 'flat notes' without the audience noticing.