When should an audio pre-amp use a differential input
If the guitar pick-up were all that were in a guitar body then it would make sense to wire it differentially back to the differential input amplifier. That's where the story ends because to make the volume pot(s), tone pot(s) and pup-switching balanced needs much more complication.

So, what about a standard guitar feeding a balanced input? No big benefit. To be balanced you need: -


A balanced input
A balanced drive - nope a standard guitar does not do this
A balanced impedance to ground and a standard wired guitar just does not do this.


So, there is no benefit wiring an unbalanced signal and impedance (wrt ground) to a balanced input. In fact you are likely to cause common-mode problems on the input because of all the capacitamce to ground through the body when intermittently touching the strings.