PF Flyers shoe sizing?

I heard from a store clerk at a shoe store that converse's and PF Flyers are made and designed slightly bigger than average shoes, therefore, I should get a size under my normal shoe size. Right now, I take a size ten in etnies sneakers, and they are somewhat roomy. I am wondering if I should buy a size 9 in pf flyers? Any advice in old fashioned shoe designs?