I agree with TheZA in that you will get a lot of opinions, but a lot of people do like DVD2OneX's compression. I have tried both Toast and it and I personally cannot see the compression quality differences that people claim so will just have to take their word on that.
The reason I still prefer and recommend Toast 9 overall is that I find DVD2OneX to be pretty much a "one trick pony" in that it is just directed towards what it does well. Toast has so many more capabilities (making custom Video-DVDs, various data disc creation options, ISO support, Blu Ray and HD-DVD support etc.) that even if I could detect the compression quality differences myself I would probably stick with it for flexibility. Unless the differences were huge of course! 😉
Another compressor that I have not tried but wanted to mention is called DVDRemaster. It comes up on video threads pretty often so might be something you want to take a look at.
BTW- while you said you want to compress it "without losing quality" that is really not an option. Any compression will result in a lower quality image than the original- it is just a matter of how much lower and to what degree you can detect it with the naked eye. All that being said- with DL disks having come down to under $1 each I still prefer that solution the most since no compression is involved in the first place! You can buy quite a few DL disks for the price either applicaton above! 😉
