Our tests in real-life applications and complex benchmarks help us chart out the preferable ways to upgrade. As we’ve found out, it is preferable to use a fast SSD in your system than to increase the amount of system memory above 4 gigabytes.
The standard amount of 4 GB is enough for most situations and adding more memory doesn’t bring any noticeable benefits. You can only get a positive effect from such an upgrade if you've got a very slow HDD in your system. The SuperFetch technology which uses system memory for look-ahead data caching may make your computer more responsive then. However, it would be wiser to spend the money to improve your disk subsystem and get much better results.
Windows 7, especially in its 64-bit version, has got an advanced memory manager that can put the available system memory to very good and efficient use. This newer OS needs less memory than Windows Vista. Even if you see in Task Manager that nearly all of your physical memory is used up, this doesn't mean your computer lacks it. This is just the result of effective data caching.
As opposed to additional RAM, a fast disk subsystem based on a solid state drive is going to be advantageous always. Besides improving the speed of disk-accessing applications, an SSD increases the overall responsiveness of the platform. The OS and applications take less time to start up and files open up faster. Although such things cannot improve your productivity much, they do make the computer more enjoyable to use.
You must realize that upgrading your disk subsystem is not a universal solution. There are some specific applications for which 8 gigabytes of system memory may prove preferable to a faster disk. For example, Adobe Photoshop can use up even 8 GB of RAM. You also need a large amount of memory to run virtual machines (like VMware or Oracle VM Virtual Box). In this case, you won’t have to stop one VM to launch another as you will be able to simply switch between them. Such usage scenarios are professional, though. And professionals do not ask questions about upgrading. They already know what they need to get higher performance.
Summing everything up, here is our recommendation for ordinary users. If you choose between different ways to upgrade your high-performance computer further, we suggest that you consider improving your disk subsystem by using SSDs. It is only if you really feel a lack of system memory and the OS’s incessant swapping makes you irritated that you should think about adding more RAM.