What’s better on a guitar? Single coil or humbucker pickups?

Depends. I think the main difference between single coil and humbuckers (besides the fact that humbuckers are hum cancelling) is output. How much output you want your pickups to have – the more you have the easier it is to drive your amp but be careful because as you increase the midrange/output of a pickup, you will also lose the highs/lows so you have to find a good middle ground.

In general here are the outputs of different pickups from lowest to highest:

—single coils—

Charlie Christian pickup (lowest) – only used as a custom order these days for some pickups companies like Seymour Duncan

Rickenbacker “toaster” pickups – only used on Rickenbacker guitars

HiLoTron – only used on some Gretsch models

Fender single coil – used on Telecasters and Stratocasters and their copies

“Lipstick” pickups – used mostly on Danelectros

Tri-sonic pickups – a unique design only used by Burns and famously by Brian May of Queen

Vistatone – only used by Supro guitars

Gold Foil pickups – used by mostly Supro/Teisco

Dynasonic/DeArmond – used mostly by Gretsch

P90 (staple) – used by early Gibson models

Jazzmaster – only used by Fender Jazzmasters

Magnetic Field Design – used only by G&L

P90 (dogear/soapbar) – used by Gibson

—humbucker—

mini humbucker – used mostly by Guild/Gibson

Filtertron – used by Gretsch

Stacked “noiseless” single coil – some pickup makers like Joe Barden, Lace Sensor, Fender and Kinman make these pickups to create a single coil sized pickup with hum cancelling

Wide Range Humbucker – used by ’72 Telecaster Deluxes and 70s Fender guitars

PAF – most Gibson models and Les Paul/SG type guitars use these

Active humbuckers (highest output) – ESP and some other brands like Charvel/Jackson may use these humbuckers and they are usually incredibly high output.