So is it better to go from a smaller pipe to a bigger pipe?

OK I know it sounds confusing so here I go. Doing some work on the washer supply lines. Well they are copper right now 1/2". Issue is there is leaking around the shutoff valves and such (old fixtures). So the question is it OK to go from 1/2 to 3/4 in piping? The distance would be about 6" for each hot and cold pipe and then and elbow then 4" to the new shutoff valve if that. Shark bite connectors for the valve and what i would be getting is 1/2 to 3/4 couplers for copper to CPVC.