As far as I know, the 305 is in fact not better than the 225. I'm unsure of the actual performance difference, but remember that the flagships have to push ~2.5 times the number of pixels that the low end WVGA devices do. GPUs don't make up for RAM in any case, what you'd be concerned with regarding RAM would be 1) any restrictions Microsoft places on 512MB devices and 2) how many apps you can keep in memory (frozen, but instantly resumable). I'm not aware of any restrictions for the first point. For the second, the phone may unload some apps from memory if you run out of RAM, but remember Microsoft has that silly seven app restriction anyway. I personally don't see 512MB as a huge downside considering the current restrictions, but if future updates allow for more background processing and more apps kept in memory, that could change.