Software support for the Marvell platform used by those Linksys routers is nowhere near as mature as for Qualcomm-Atheros hardware. It's improving, but definitely hasn't seen the kind of thorough widespread testing that QCA platforms get.
This comment is correct. Atheros was a long-time Linux/OSS friendly-ish vendor, where Marvell isn't. Marvell has been making some positive moves, but they are still GPL violators and don't work with the community like QCA does. That being said, some Marvell-based routers are pretty well supported now, like the Linksys AC1900.
