Cost is always a factor in any decision but the headline costs of the switches is only part of the consideration.
When you are faced with a cost comparison between switch A and switch B from different vendors it is important to look past the upfront costs and factor in the support costs as well. If your current infrastructure is Cisco then you have people with Cisco skills and this is an important factor.
You are the one that is going to have manage these switches not the consultant.
I have worked on large networks and from previous experience if we had always gone with the cheapest option we would have ended up with a lot of different vendor switches, each needing to be supported which would mean people having skills in that vendor.
And each having a different management platform etc.
In addition, as Leo mentions, with multiple vendors you often find them passing the buck between each other when there is a problem with your network.
That doesn't mean you have to buy everything from one vendor because there are times when a certain vendor's equipment has functionality that others don't and then the decision is fairly straightforward.
But what it does mean is if you have standardised on one vendor then you need a good reason to use another especially in something as important as your base infrastructure and upfront cost alone, although important, should not be the only factor in the decision.
I have never used AT switches so I can't so anything about them but one thing I would say in terms of support is that Cisco does really well in this regard not just with technical documentation but also with forums like these.
I am not trying to talk you into buying Cisco, that's not what these forums are for, but in the end based on what you need the switches for there may not be a good technical reason that points to one vendor or the other, so it will come down to other factors.
Jon
