^Except that DL media, even Verbatim, isn't as reliable long term as single layer dvds. The extra complexity in the physical structure of the DL disks makes them vulnerable to failure. Just a fact.
And if you are going to compress with a transcoder, there really isn't too much difference amongst them. They all do an acceptable job at low compression rates. So you might as well use a free one like DVDShrink. Just don't push them....too much compression with a transcoder will lead to very poor results.
If higher quality is your object, then the encoders, like HCenc, CCE and Procoder are the tools to use. Though even they have some differences in output quality as Wombler pointed out. At this point in time, I don't see any reason to use any mpeg2 encoder other than HCenc. This free mpeg2 encoder has caught and surpassed most everything on the video enthusiast market. There are some that are slightly better, but with those, you are entering the professional level, with corresponding HIGH costs.
One of the main drawbacks to using an encoder used to be the extra time it takes, but with modern, multicore computers, HCenc runs through dvds in very little time at all. DVDRebuilder is a good gui for HCenc, either the free version or the Pro version, and it is the gold standard for dvd backups these days at the amateur level.
So if you are simply backing up dvds and keeping them in dvd video, the only compelling reasons to use anything other than the free software is if you need updated decryption to cut through the newer protection schemes as they come out, or if there are some extra capabilities in the commercial software that meet your specific needs.
Even then, software like DVDFabHD Decrypter or BDLot ISO Master combined with DVDShrink and DVDRebuilder are hard to beat. Impossible in my opinion, if the only thing you are trying to do is make smaller backups of your dvd video.