Generally speaking the 512MB GDDR5 is going to be better. The GT 440 is not fast enough to really benefit from having 1GB of RAM. The faster memory on the GDDR5 card will give you better gaming performance. If you are running high resolutions, you would want at least 1GB of memory for gaming, but the GT 440 simply isn't powerful enough for high res gaming anyway so that point is pretty much irrelevant.
If you're not gaming it really won't make a difference either way. Basic desktop applications and video playback aren't effected by the amount of memory or memory speed on the cards available these days, either will be sufficient.