VMware versus Hyper V.
I struggled to find a decent unbiased comparison of VMware versus Hyper V that dealt at the SME level (Vmware Essentials Plus level for instance). Often sites would say something along the lines of "Hyper V is getting better but Vmware is still the only one to recommend" without much more detail or they wouldn't be comparing the latest versions. All Hyper V articles don't seem to say there are any deficiencies with it (until the next version comes out when they say things like "this is a feature that users have been crying out for" etc).
I'm sure there are decent sites out there with in-depth reviews but I struggled to find them when I was looking before settling on VMware, but would've been willing to give Hyper V a go.
The really difficult thing with VMware that I found (when researching about 18 months ago) though was the naming. They seemed to have changed the name of the products so often and had such a range of individually name components (each feature having a brand name) with little explanation on their site - Vmware server, ESX, ESXi, vcentre... web interface, vcentre client. They really seemed to expect you to know exactly what each product was with little in the way of a decent introduction.