Generally speaking, a "K" at the end of a DeWalt model number means that the tool is part of a kit that includes a plastic carrying case. Model numbers without the "K" are just tool and an accessory or two like a blade, blade wrench, etc. An "R" in the model number means that it is factory reconditioned. Reconditioned tools are ones that get returned to a retail store or the manufacturer for one reason or another. They get a complete teardown and once-over before marked as reconditioned and sent out the door again. Because of the second set of factory personnel going over reconditioned tools, I know a couple of people that will only buy DeWalt if it's factory reconditioned. If a reconditioned tool is bought from an authorized DeWalt dealer, it will have a warranty which varies from tool to tool. Looking at DeWalt's website, the specs are identical. I suspect that the slow blade speed discrepancy is a typo.
http://www.dewalt.com/us/products/tool_detail_listing.asp?categoryID=1410