Its roughly x1.5 stronger than Hydrocodone so it will be slightly stronger if you take the same dose. The high is also a little different. I find that Oxycodone is more stimulating and Hydrocodone more sedating.
First of all, I wouldn't say that 20mg hydrocodone is a medium tolerance. It's quite low. As far as taking percocet: If 20mg of hydrocodone gets you where you want to be, take about 15mg percocet and that should suit you just fine.