I have both (we bought the 210s before the 435 was released), the big killer for me is that the 210 hasn't had any software updates in nearly three years (last update was April 2019), while the X435 is running a nearly full EXOS (it's missing nodealias for some reason) and so should get decent support for a while. The Fastpath CLI is OK but I generally use the web interface on the 210s anyway. No build quality issues that I'm aware of.