Cisco comparison is a bit silly
Yes the currently shipping Nexus blades have 32 ports of which only 8 are available in 'dedicated' non-oversubscribed mode, but that's a first generation card. There's a 32 port non-oversubscribed one due in a couple of months - still only 256 ports I know, but I doubt Arista has shipped any of these yet either. So you'd only need a pair of Nexus 7010's or one Nexus 7018 to reach 384 ports. The Cisco also has a modular backplane, and a roadmap for a lot more performance.
Granted I'm sure the Arista will still be much less expensive.