Subject says most of it. 
I have read the physical networking “best practices” guide, and I am currently running a small (3-node, NX-1175S-G7) cluster on top of Dell S4112F switches.

My org is looking to add a second cluster at a second datacenter, and I was asked if the Mikrotik CRS510-8XS-2XQ-IN or Mikrotik CRS518-16XS-2XQ switches would work for the new cluster.

My initial response was “no,” but I’m wondering if anybody has tried it? I would be concerned about buffer size on the switches… but how much does that matter if all of the cluster nodes are connected at the same speed, and I have a L3 boundary (router/firewall) between the VM subnet and the rest of the network (router has much better buffering than any switch would)?

I do not have decision-making power here, so how can I “influence” my boss that using three-figure switches is likely to be a problem for a 5-figure+ cluster?