The CSS610-8P (and CSS610-8G) is built based on the Marvell
88E6390X switch chip.
SwitchOS lite runs on a small CPU integrated into the switch chip, what makes the very low price point possible, compared to other brand's managed PoE 2x10GB switches. But the drawback is it has not enough resources to run full SwitchOS or even RouterOS.
Technicaly, the RB5009UPr+S+IN is close to a C
RS610-8P. It contains a slightly better switch chip (
88E6393), combined with a powerful CPU and enough Flash/RAM to run a full featured RouterOS.
Granted, it only has 1 SFP+ port, as one of the switch chuips's 10G ports is "wasted" for the 2.5GB ether1. But beside that, it is pretty much a router version of the CSS610-8P. And it fits into 10" and 19" racks.