The Asus will be better because it has a quad core CPU vs the low power consuming dual core CPU in the Dell. However, the i7-4710HQ consumes 3x more power which will have a detrimental affect on battery life. The GTX 850m is a bit better for games than the GT 750m. You will need to decide what is more important to you... battery life or performance.
For typical office use like Excel, e-mails, Word documents both laptops are suitable. For CPU intensive task like data mining a database or running Monte Carlo simulations the Core i7-4710HQ will provide better performance.
My main aim is to install vmware workstation & on top of it create 3 virtual machines of windows server 2008, windows server 2012 & Red Hat Linux to practice Windows Active Directory Services (AD) & vmware vsphere.
What about Lenovo 59-417149-Z5070-WH -- 15.6" Core i7 4510U 1.8ghz Ram - 8gb 1600 Mhz expandable to 16gb, 1TB HDD Nvidia Graphics card - 4gb?
I have no experience with VM, but I would say that the quad core i7-4710HQ is the better choice especially with more than 1 VM running. I would also assume AD is pretty CPU demanding as well since it is usual run on a server.
I think it is best to get some type of workstation laptop that would fit your needs, or a laptop capable of installing more than 16GB of RAM. Since I am not in the IT profession I cannot give advice based on my own experience. I can only recommend that you speak to the IT department (unless you are the IT dept.) or to your professional peers to give you better advice.