Absolutely test thing out to see which works best for you. I would say the biggest mistaake I've made while selling on ebay was shipping also. i wanted to make sure people got their items as quickly as possible so I always used priority mail. Now I know that parcel post or first class mail is the way to go. I really don't think people expect to get there items in 2-3 days unless they request it. More often than not buyers will opt for the cheaper option!