I've been involved in this hobby of digital media for quite a few years now. Every few years some group of people get interested in making their files smaller. Generally by changing the format and generally by reducing the quality of the media. Sometimes this involves a different CODEC.
In your case, you are using a more efficient CODEC that is probably giving you a large reduction in file size. But are you preserving absolutely, positively, all of the quality of the original source? Maybe yes, maybe no. More often than not, in my experience, trying to find the line where you preserve all of the quality, yet reduce the file size, is very very hard. ...and most people find out the hard way that they have NOT preserved all of the information present in the original. Some of it is gone. In video this becomes more obvious with large screens, complex video, and lots of motion. You wonder why the scene with high motion shows macro-blocking on your large screen. You go check the original and it's not there. Then you know that your reduced quality and size copy has lost something.
Storage continues to get more and more dense. Prices continue to drop. In my not so humble opinion, chasing small file sizes is foolish. You will NEVER regret having the original. But you are likely to regret your reduced quality copy. Save yourself the time, effort, processing power, and headache of trying to reduce file size. Just keep the original and be done with it.
This is all just my opinion and you can certainly ignore me if you disagree. Best of luck with your digital media collection.
Brian.
