In answer of a single line it will be NO. Only the right thing about More RAM means more multi tasking. If you are doing more tasking or opening many windows at one time then you may need to upgrade your RAM for beter and smoother performance. Otherwise if you doing one or two tasking at one time then you will no need of upgrading your RAM. There are some applications like Virtual BOX and Photoshop with whom you are very much clear and friendly are basically took more memory to run as they have to perform various tasks inside them. Upgrading RAM on your system means increasing the space to your machine to do more multi tasking.
If you are doing one task which consume 200mb RAM and your pc have a 2GB RAM installed then upgrading it to 4GB RAM will note make it faster in any way. Now it on you to very much clear on the matter wheather you have to change your RAM or not. Just go to task manager and check how much memory your system consuming, Is it near to reach the limit to 100%. If yes then only you need to change it. Take in Mind for general purpose a 2 to 4 GB of RAM is sufficient, but if your are playing games, doing virtualization or Using video editing tools etc then you will need more RAM to be installed.