as above said, when performing, its important to be used to standing.

but sitting makes playing ALOT easier and more comfortable. like theres some shred solos that i just CANT play standing up because of how my guitar is set up, how i hold it standing, etc. it just takes work.

usually, i learn and perfect a song sitting, and then when im extremely comfortable with it i learn to play it standing up. and then you gotta throw in all the fun stuff like dancing and jumping :p