What's the meaning of the title?
720p as in "720p resolution panel" or 720p as in "720p encode"?
If the question is regarding the panel itself, then 720p at 42 inch should be enough if you dont mind seeing the pixel structure, or if you sit far enough - from around 2-meters away or farther. But during the past 3 years or so, major CE makers have stopped any significant improvements on 720p panels, thus, napag-iwanan na ng panahon and technology.
If the question is regarding the quality of encode compared to the source, based on my observation among PDVD friends, there is a good percentage of people who like having nearly 300 titles in a single 2TB, but there is also a good amount of people who'd rather have around 150 titles in a single 2TB, and finally, there are some who would prefer to have barely 50 Full BD rips within the same 2TB. Since all of those people seem happy, that means whether 720p or 1080p or Full BD - No Problem La - basta maganda ang encode and more importantly, maganda ang titles. Yeah, although I personally prefer to watch Full BDs, I'd say 720p encode for a 42 inch (or even 50) is enough. Maski nga WEB DL quality, very tolerable pa rin basta maganda ang HDTV.
Some people claim to see the difference in resolution between a 720p encode and a 1080p encode? Really? Sabi nga ni Pugo, Dasalasanansens! - IMO! hehehe. A brilliantly encoded 720p only needs to be magnified 2x in order to fit a 1080p screen. If the quality of a 720p encode is decent enough, that much magnification would not deteriorate the image quality to the point that it becomes crap and completely distinguishable from a 1080p encode - ESPECIALLY, if you have a very very very very very very very very very good HDTV.
In my observation, the discernible differences between a 720p encode and 1080p encode are as follows:
1. Color saturation - lowering the bitrate makes the color "less rich". But then, if you don't have the master Bluray source playing on the side, how can you establish a reference? And also, there are Blurays which have generally dull, or dark colors, that even the master look kinda crap. On the other hand, there are also contents which are extremely colorful that no matter how much an encode gets compressed, remains colorful enough.
2. Compression artifacts - blocky parts, all sorts of blemishes, jagged edges here and there which are easily visible in monotonously bright areas of the image or at the edges.
3. 720p encodes would generally have less grain, thus fakely cleaned image - because grain requires a lot of bitrate. If the source is too grainy and the encoder wants to remain transparent to such graininess, he must increase the bitrate as much as he could - thus resulting in a bigger filesize.
The main objective of prime (internal) encoding groups is to remain as transparent to the source (colors, grains, sharpness, image cleanliness, etc.) as reasonably possible and as they technically can, by manually manipulating the detailed encoding settings of the X264. I understand that a "good" 720p encode takes at least 72 hours of non-stop encoding, while those fast scene/public releases under automated encoding settings can easily finish in hours. Hence, a brilliant 720p encode is soooo much more challenging to make than a 1080p one, while a Remux is the easiest.
