It depends on you, the only difference is the internal space. The whole internal storage can be used for apps unlike most other android phones. If you install lots of HD games which has been taking more and more space nowadays even 1 or 2gb of extra space, you'll want the 32gb version as you can't move apps to the sd card on the s3 without doing some modifications to the system.
I certainly think it's worth the extra money, don't know about you though. I have teh 32gb version along with a 64gb micro sdxc card haha XP

I'm thinking of switching from iPhone 3G to Galaxy SIII..

But i'm a low monthly user.. currently on Celcom family plan with monthly usage max of RM20.. do u think i should buy SIII without plan at RM2199 or sign a plan?

If I buy at Rm2199 then I can just add on Rm38 for the monthly 1GB internet plan