Single vendor is a support decision, not a purchasing one

There is a persistent idea that a network should be one manufacturer end to end. On a large campus with a support contract that can be true. On most projects it is an expensive habit, and the money it costs buys less than people think.

The useful line is not between vendors, it is between layers. Switching, wireless, security and cabling can each be sourced on their own merits without anyone being able to point at the seam. Within a single cabling channel, the line is real: cable, jacks, patch panels and cords from one system, because that is what a manufacturer's channel warranty is written against, and mixing inside the channel is exactly the case a warranty claim gets refused on.

Said plainly, the question to ask on every line is who has to answer if this fails. Where the answer is one manufacturer, keep the layer whole. Where the answer is the integrator or the desk, buy on merit.

Everything on this desk is authorised and genuine, whichever way a project splits it. That part is not a preference.