I was just working on an embedded project myself (albeit Zynq based) and we decided to steer clear of eMMC. The main issue with eMMC is that the greater the bit-density, the lower the lifespan. They're doing better with some of the new technologies, but I'd still be worried about memory failures if you plan on the product lasting 10 years. If you do go with eMMC, try to see if you can get away with SLC. It doesn't have much memory capacity, but it will generally last longer. As some of the others have said, socket and SD is really the best option though.