Only way I can answer this is to give you an idea of my personal configuration and experience.
I do a lot of web application development and use a single box for the whole thing.
Core i7 3770
RAID 10 128GB SSD
1TB HDD (music and pictures)
My primary OS is Windows 8 Pro. I'm running 3 Virtual Machines Two of the VirtualBoxes, Windows XP and OSX Server, are used to test the application across different browsers.
I then have my development box which is Ubuntu 12.04.2 which houses my web server and database server. All three VMs are installed on my RAID10 SSD which is nightly backed up to the 1TB as well as to my WHS2011 server. (Double reads, but beats data loss)
I use Samba on the Ubuntu VM so that I can map a directory on my Windows 8 Pro OS. I do all of the development in Windows 8 Pro (primary OS). I use KiTTY (alternative SSH program to PuTTY) to SSH into my Ubuntu box to execute any necessary scripts/commands. My editor that I primarily use is Sublime Text 3.
I have a 5 monitor configuration where I use
Bottom left for the SSH terminals
Center for Sublime Text
Right for testing locally on site and database access (PHPMyAdmin)
Top Left for Music and Email
Top Right for split view on the two other testing VMs.
All VMS are in bridged networking mode for ease of networking.
With everything running at time of development and testing, I'm using 1/4 of my CPU and 1/2 of my RAM. I have plenty of HDD space remaining and couldn't ask for a easier setup.
I've been down the same road as you. Should I just run Ubuntu as my primary OS since that is where my applications are being developed under... I have struggled with this question time and time again. Yet, I always find myself going back to Windows as the primary OS and using Ubuntu in the VMs. I'm very well versed in the linux environment, but there are just little annoyances that keeps me going back to Windows. Plus, some of the applications that I'm required to use from time to time only run on Windows.
Best advice that I can give is to stick with what you're most comfortable with and what feels most natural.