VirtualPC 2007 + VirtualBox + VMWare Player. All three working together on one system, just not at the same time.
I would wager that a lot of the respondents to the poll work in VMware-biased companies (unsurprising, as VMware has been in this field longer than Oracle and Microsoft put together), and once you get sucked in to VMware, it's not exactly easy to break out of that box. Throw in that you can now *create* VMs in the free VMware Player, and it's just gotten harder. I have two issues with VMware - it's highly proprietary, AND it's rather pricey for SMBs and non-profits. Oracle VirtualBox can run on any hardware that supports VMware, yet can't support Hyper-V due to lack of EPT; further, as long as you stick to using the VHD formats for virtual hard drives, you can trade VHDs with Hyper-V (clients or servers) or even VMware. If your hardware CAN support Hyper-V, it's attractive due to the lack of cost - it's included with Windows 8 or any version of Windows Server as old as Server 2003. What suits your needs depends on what sort of client support you need.
Modern laptops uses usb 3.0 so , I think vmware is better than virtualbox because the vmware supports usb 3.0 but the virtualbox does not support it yet ! I have installed latest version of both of them to use all of the features of Virtualization.
I use VMWARE WS for MAC 10.82, and VirtualBox for virtual server, with plataform Windows 7 Ultimate x64 SP1...but not use both for my works.
VMWare Player/Workstation are the best solution out today. They're the only ones that can successfully run Visual Studio 2013 + Windows Phone SDK + Windows Phone Emulator. The latter will not run on the other virtualization platforms due to lack of CPU Intel VT-x support. No significant differences between the two VMWare products other than snapshots, which saves a lot of time when rolling back to a prior, stable state. Otherwise, you can accomplish the same by zipping up the entire folder for that virtual machine prior to making changes you may want to revert - slower than snapshots, but works the same. Naturally, if you're running Mac OSX on a PC, Workstation is preferred for the various tools out to enable that on a PC. Right now, have noticed VMWare Player 5.01/5.02 has a memory/virtualization leak of some sort. If you run ThinApp in it often enough capturing snapshots and such, there's the rare primary OS freeze requiring a full 4-second power button shutdown to reboot. Haven't seen this with <v9 Workstation versions at all.
I am using both VM Ware and Hyper V and both have different features. Because VM Ware is the first in virtualization, so have more features and solutions than MS Hyper V.