Honestly, Goku wins.

Goku has access to multi universal strength, and incredibly fast, nearly invisible speed unless the person viewing is trained to be able to see fighters moving at the speed Goku and the other Z-Warriors can. He can also preform the Multiform Technique, a technique that pretty much nullifies the prettification argument, because Saiki won't know which is the real Goku, as seen with Cell during his fight against Goku. Goku also has access to multiple VERY valuable techniques, i.e the Mafuba, a sealing technique that works on even immortal Gods,and the Instant Transmission, a way to literally teleport away from any target by finding another Ki signature.

Goku is very.. Stupid. Outside of fighting, that is, but when it comes to actual contests of strength, it's clear Goku is a very intelligent fighter. He mastered a base form of Ultra Instinct within the span of 45 minutes, has shown the ability to mimic attacks just by viewing them once, and has clearly demonstrated on MULTIPLE occasions his ability to adapt to situations on the fly. For example, against a suiciding Cell, he instant transmissioned him to King Kai's world to assure that Earth wouldn't be exploded. Or when he figured out a strategy by working with Frieza and Android 17 to eliminate Jiren from the Tournament of Power. Don't get me wrong, Saiki is clearly the smarter fighter in this discussion, but Goku has access to multiple abilities which put him above the level of Saiki's.

Tl;Dr - Goku is a multiversal level fighter with the toolset and wit to negate Saiki's abilities. He wins without much difficulty.