There’s probably two questions here – should you, and would you…
Depending on the scenario, possibly yes to both!
VMware best practice says use VMXNet3 unless there is a driver or compatibility reason not to. Despite this, when you deploy a new VM it still defaults to E1000 NICs and it is down to the user to specify. Supposedly the reason is that E1000 has broader compatibility across all operating systems, so default to the one that will definitely work, not the best. Plus, the majority of OS’es have baked in drivers for the E1000 as it’s an emulated Intel NIC.
There’s an excellent overview of the differences between E1000 and VMXNet3 here.
That being said, if the VMware guidance is to use VMXNet3 unless you can’t – the NetScaler firmware has supported VMXNet3 since an 11.0 build 65.31 – so the answer is yes – you should.
Now, would you? Well, the main pay-off for changing to VMXNet3 is that it is a fully virtualised NIC, not an emulated one which allows for superior network performance – e.g. if you are deploying a VPX-5G, 10G or 25G then you have to as only VMXNet3 will support this volume of throughput using SR-IOV.
Now if you’re deploying a NetScaler Gateway @ 45Mbps or a VPX 10, 200 would you? Probably not. There are always anecdotal issues around “I changed to VMXNet3 and now my NetScaler drops off the network every 5 minutes, and catches fire while users hunt me down for revenge” – you won’t typically get these issues with the E1000 as it’s emulated so arguably will be more consistently presented to the NetScaler, so less issues (in theory). Obviously your mileage may vary and there are certainly several documented “issues” that are resolved by switching from E1000 to VMXNet3, but as always you have to tackle these as you find them.
So do you need to change to VMXNet3? Maybe 🙂