Why would the Samsung Epic 4G have better reception than the iPhone 5 at my house, when both phones are using the same Sprint service?

I recently changed phones, from a Samsung Galaxy S Epic 4G to an iPhone 5. I kept the same Sprint service. After changing phones, I found that the reception in my house with the iPhone 5 was considerably poorer than it was with the Epic 4G. In fact, my iPhone is next to useless for talking on the phone when I am at home, whereas I rarely had a problem with the Epic 4G.

I think it’s safe to say that Sprint's signal strength at my house hasn’t changed. With both phones, I saw about the same number of bars (one or two), which makes sense to me. In addition, my wireless network (run by Time Capsule) has not changed. All that changed was the phone ... and the quality of the reception.

Any ideas as to why the Epic 4G had better reception in my house than the iPhone 5? Maybe I just have something set up wrong.

Thanks.