Is battlefield 4 or battlefield 3 taking longer then a minute to load? If you upgrade to a SSD it will bring your load time down to 30 seconds. If the performance and boot up time of your computer is your primary goal, then you should buy a solid state drive.
Hdd vs SSD Load Time Comparison Video
As you can see the difference between a hdd and ssd is huge! I recommend to buy at least a 120gb ssd. You can even install your windows on the ssd and your pc will be even faster. you will be playing battlefield 4 on your new SSD just in time for the release of Second Assault.
Here is a link with more information and differences between a solid state drive and a hard disk drive.
The Best Solid State Drives For Your Money