Is it better to stick with Max Knuckle for the attack boost or is the Crit boost from G-Max Chi Strike better than an attack boost? I would use this Machamp for Wifi battles.
Dynamaxed Machamp is better than Gigantamaxed Machamp. In your three turns of being Dmaxed, you can get a solid Attack boost. However, the increased critical hit chance is not guaranteed -- you can still have an attack without the crit.
So Max Knuckle is better, as it provided a guaranteed Attack boost each time you use it. G-Max Chi Strike is less reliable.
Hope I helped!