DanLights
Santa Hat Forever
I voted for guitar.
Recently recorded a shitty Epiphone with stock passive pups, the DIs were terrible.
Then compared it to an ESP that had EMGs - difference was huge and it was much easier to dial in a tone.
Best to start with not just the weakest link in your chain, but start at the start of your chain!
From your post, you should´ve voted Pickups, not guitar.
Edit: I tought pickups were a separate choice from guitar, sorry.
I say Guitar preamp, it gives the tone and is the most recognizable I say. You hear a tone and you say "That sounds so much like a Rectifier", you don´t say "that´s mahogany wood, I can bet my balls on it", at least that´s my case. Specially if it´s heavily distorted guitar you´re talking about, it´s the preamp that gives the distortion tone, with everything else adding or substracting from it.
If it was clean guitar, you could say you depend a lot more on the wood of the guitar, the pickups, the cab, while the preamp is more of a typical colortion than the whole tone.
Just my thoughts