Core and data center applications are the strengths of Arista products. The distribution layer is also a good fit. For the access layer, it would be more of a niche product.
Huawei Ethernet Switches are perfect no-nonsense network switches that can be used in any internal network. They are especially helpful if you require PoE functionalities or if you need to configure network settings manually (e.g. static routing, VLAN). There are no real-life situations I can think of where these switches would not be suitable
The switches perform very well in our core backbone and also in metro Ethernet networks. We are able to provide high service availability and greater resilience for our customers. The switches also provide high performance in several data centers where we have a presence focused on IX exchange. They are also very useful as CPEs.
I have used the Catalyst 6500 series in the past. From my point of view, the Arista surpasses the Catalyst on just about every front. Originally we were planning on implementing the Nexus 7000/7700 series switches for our core. Though a little more feature rich, it did not provide features we needed that the Arista did. The Nexus also was a confusing and complex platform to work with. Also, the Nexus was a significantly more expensive solution. Although very happy with the Arista switches we may evaluate the Aruba HPE 8400 chassis-based switches along with Arista switches in the future.
The performance of Huawei is lower than Cisco, but initially the costs inclined the decision towards Huawei, but unfortunately, it was not, the licenses and the manager fired the investment to make it very similar to cisco. Therefore it is preferable to go to the Cisco switches for reliability and robustness.