RX100 10MP mode = reducing 20MP in PP?

So I noticed in the manual RX100 has 10MP mode which might be better for me as I don't intend to print huge prints. So, my question is whether 10MP mode would preserve the detail/quality the same way as reducing the image size in Photoshop from 20MP?

http://www.sony.com.hk/svcfiles/faq/DI/User_Guide_Eng/DSC-RX100/contents/04/02/01/01.html