Well...
3GB>2GB
1GB>512MB
Maybe if you could copy the links of those models from a webshop, so that we can see the whole specification and the price. Or at least the links to the models on the makers' websites.
You can ask people if Sony or Dell is better. Surely there are objective measures to say one is better than another. But there can be many things to be taken into consideration like
- PRICE,
- length of warranty (3years vs. 2 years can make a big difference!),
- quality of the parts (watch youtube videos about your model, see if they have typical failures reported by many people),
- quality of the customer service (well horror stories rulez, I mean they are not always reliable, but...)