Replacing hard disk with SSD or increasing RAM in MacBook Pro I am using MacBook Pro for the last 1.5 years. Here is my configuration.

13" MacBook Pro, min-2010
2.4 GHz Core 2 Duo
4 GB RAM
OS X Lion 10.7.4


Would you recommend upgrading to SSD for fast processing or would upgrading RAM will be better?

I am also worried about my pocketbook. 320 GB of hard disk can be used as external hard disk after upgrading, but in case of RAM previous RAM will be useless, as the Macbook Pro only has two slots. (Currently both are used, 2GB RAM slots each.)

PS: I am a Ruby on Rails and iOS developer and using my MacBook Pro more than 15 hours a day for coding purpose. I have the 2 year extended warranty.
It depends on how much RAM you're using. Use something like iStat Menus or MenuMeters to keep an eye on your RAM usage.

If you're constantly near or over 4 GB RAM used (wired+active), more RAM will be the better option. (You can also tell this by seeing how much swap space you use; if it's over some nominal value like 64-128 MB get more RAM.)

If, on the other hand, you never even get close to 4 GB of RAM usage, get the SSD. Or, get more RAM anyway and use the excess as a ramdisk, which will be way, way faster than an SSD.