Hello, 
I have this ind of situation.

Source env:
It is vSphere 6.5 (both vCenter Server appliance and ESXi hosts) where I have an admin account to connect to, but currently only to vCenter and not to the ESXi hosts

The VM to be migrated is Windows 2008 R2 SP1 with virtual hw version 8 (ESXi 5.0 and later) and has one boot disk 35Gb and one data disk 250Gb.
The SCSI controller is LSI logic sas and network vmxnet3
It has no snapshots at the moment

I see in my oVirt 4.1.9 that I can import from:

1) VMware

2) VMware Virtual Appliance

and found also related documentations in RHEV 4.1 Virtual Machine Management pdf
Some doubts:

- what is the best between the 2 methods if I can chose? Their Pros&Cons?

- Does 1) imply that I also need the ESXi account? Currently my windows domain account that gives me access to vcenter doesn't work connecting to ESXi hosts

- also it seems that 1) is more intrusive, while for 2) I only need to put the ova file into some nfs share...

Thanks in advance,

Gianluca