Do 50g films have better PQ then 25g films?

[CptGreedle]

A movie can fit on a 25GB disc no problem and still look great too, but it would have to be short. For a long movie (1 1/2 hours is long enough), a full 50GB disc would have the room for the information to spread out. That will avoid compression which is used on all video, and can provide uncompressed and lossless sound too, which is on MOST BD titles.
Without the extra space, you will probably have to compress sound and image, especially for longer titles.
It is in NO WAY overkill. BD50 discs tend to get better reviews, and games are already using more than 25GB. Imagine putting a long movie like Lord of the Rings on a 25GB disc and you will see tons of compression and lossy audio. But with 50 GB you can fit lossless audio and better video.