As stated, every vendor has its merits. If you really put some time into developing a list of requirements and then structure a bakeoff that tests those, you will learn a lot.
Some things to think about:
* don't let JUNOS or any other CLI deter you. You just need to factor in training and hiring efforts/costs. We switched to Juniper for 50+ campus routers (haven't used their switches yet) because they had way better bang for the buck. The engineers that whined about it not being Cisco were not the ones I cared to keep. The engineers that went out and learned JUNOS then slapped it on their resume were, by far, the more reliable and skilled engineers. Also, when you are hiring, I bet that you will find that engineers with substantial experience in other platforms will also perform very well on the technical interviews. They will probably know advanced BGP, MPLS, tunneling, multicast, QOS and other stuff that your average interviewee does not. It's a mindset.
*politics: we replaced a large section of our network with Foundry (a price-per-port) decision. They worked as well as any vendor out there, but their support was... not polished as Cisco or Juniper. But the real problem came from the low level support engineers who had a CCNA and were Cisco-oriented. Now, when we had Cisco blade/power/code failures, it was a "network failure". When the Foundry had a problem, it was a "Foundry failure". I watched a huge outage due to a poor spanning tree design get branded as a Foundry issue. Management hears this enough and eventually we are told to replace the Foundry switches. I pulled ticket logs and proved that the support team had nearly twice the amount of open tickets and logged failures with Cisco as they did with Foundry, but it didn't matter.
*politics again: If you are a big cisco shop and you decide to use another vendor somewhere, I GUARANTEE that a regional sales VP and some ducklings in suits will soon walk directly into the CIO's office. They will argue that the bakeoff was skewed, that price-per-port value doesn't factor in a lot of other value that cisco brings, they will even question the skillset of your engineers who performed the bakeoff, etc... they will instill Fear-Uncertainty-Doubt. They will offer another 2 or 3 % discount, they will throw in free professional services, and so on. Hell, they may put a Cisco employee on your board of directors. Short story - if there's a lot of money involved, you may wind up back with Cisco. I've seen it more than once
That being said, I don't dislike Cisco at all. Their support is top notch and their training is pretty good. They take good care of their clients. A LOT of their products are good... some are not. But I did want to prepare you for the fun if you seriously consider another vendor.
We have selected Mellanox for a small data warehouse, but that was a point solution due to the Infiniband requirements.
We have selected Arista for a large Hadoop deployment. So far, they are a great product and a great value. Support seems good, but we haven't called them much yet. That's a good thing.
One other thing to consider is future state and emerging technologies. If you are an architect or if you work with architecture to obtain design direction, ask about future needs for multi-tenancy, SDN, automation and such. I think you'll find that not only is Arista way out ahead of some vendors with this, they are using Open source code, more or less. Cisco has onePK, but their automation and API integration is not only proprietary, it's misleading. I haven't seen the other vendor solutions yet, so I can't say who is BEST at automation, orchestration, and SDN...
So... determine what's important to your network today and in 3-5 years, then look at what's being offered.
cwb