Serv-U MFT Azure Server Requirements

We are running Serv-U MFT on an Azure virtual machine that is a general purpose setup.  (DSv2)   

Our MFT server is handling a very high volume of connections, (1.2m per 24 hours).   This type of connection volume is causing customer connections to be slow and in many cases blocked.  

I'm looking to change our server type and add resources to see if this helps before switching products.   Given the options below - is it better to go F series, or E series?  

What would you all recommend?