video converting help

I'm kinda new to toying around with video files (ripping, burning etc.) I use mactheripper to rip dvds, and often times i use roxio toast to convert the video_ ts folder to an mp4 file. I was told that was the best way to convert the video while keeping video quality and also save space. Usually i get a them down to 1.5 gigs.
Lately i have been downloading torrents of movies and noticed that i have been getting avi files of movies about 700mb. Some of these movies look better than the ones i convert to mp4 with toast.

My question is if my way was the best way to handle these files. is there something else i can do to convert videos without having the video quality suffer. I use roxio toast 9 and it has many converting options.

 

thanks for the advice,

I've used handbrake in the past but i just seems to take a really long time to use. even to just encode one chapter.

When i use roxio toast to convert videos it says it's using the h.264/avc codec in the video summary. It just seems like some videos have quality that arent great.