If you look at the training requirements under Part 121, PICs and F/Os get almost the same training. They are in class together so they'll have the same classroom training. They are normally paired together in the sim. The difference is the oral exam won't be as long (do you really care if the F/O can explain the difference between a momentary action switch and an alternate action switch) and there are 4 less manouvers on the check ride. No steep turns, no zero flap landing, no jamed stab approach and go around and if you have more than 2 engines they don't have to do the two engine out approach and landing.