It's better to use FEX in Cisco ACI or not?

[Va.8427]

Hi there. 

Assume that, We are going to implement a new data center including almost 26 Racks, based on Cisco ACI technology.

I'm a little bit confused whether It's better to use FEX (such as 2348UPQ) as Top of rack and thus decrease the number of leaves or not. what are the caveats? what features will i lose? 

[richmond]

There are some features that are not supported but not many and as releases go by it is getting closer. 

However I would not recommend using FEX in a new install. You will have very limited  TCAM available if you try to push multiple top of rack switches into a single parent leaf switch. You will get much better scale out of the network by using Nexus 9K leaf switches and not FEX.