This is true. Someone who wants to run lots of apps simultaneously might find the 1GB of RAM on a S3 limiting, especially given the additional overhead of TouchWiz. It's less of an issue with the S4 Mini (1.5GB), Moto X and N4 (both 2GB).
The International S3 LTE has 2GB of RAM. I had that before my N4. Having more apps running means more battery usage, and more recharge cycles. I use my phone a lot, but when the screen is off I'm made it so pretty much no apps poll the net (I only get push notifications).