Ok firstly here is a bit of info on tagging for Bluray ripps so you you can see the difference in scales of quality.
Similar to DVD-Rip, only the source is a Blu-ray Disc. A BD/BRRip in DVD-Rip size often looks better than a same-size DVD rip because encoders have better source material. A common misconception among downloaders is that BDRip and BRRip are the same thing. They differ in that a BDRip comes directly from the Blu-ray source, while a BRRip is encoded from a pre-release, usually from a 1080p BDRip from another group. BDRips are available in DVD-Rip sized releases (commonly 700 MB and 1.4 GB) encoded in Xvid(AVI) or x264(mp4/MKV).
BD/BRRips come in various versions: the m-720p (or mini 720p), which is a compressed version of a 720p and usually weighs around 2–3 GB; the 720p, which usually weighs around 4–7 GB and is the most downloaded form of BDRip; the m-1080p (or mini 1080p), which usually weighs a little bit more than 720p; and the 1080p, which can weigh from 8 GB to sizes as big as 40–60 GB. There are also mHD (or mini HD) versions available, which are encoded in lower resolution and are smaller in size.
As you can see BDrips will be the best quality but will be a lot larger in files size while you can get BRrips in very small size, and both can be encoded into and of the 3 most popular video formats, AVI,MP4 or MKV.
For the difference in quality for these 3 video types it really depends on how compressed the origianl source file was before rencoded into a smaller BRrip, and how compressed the newfile is, even how good the uploader is at making BRrips. It really makes no difference what type of video file is used thats really a personal preference on which file type you prefer, and the source you download from.
You ask what is the diffference between BRrips and non BRrips, well again it's not to do with the video file type it has to do with the origianl source used and how good the uploader/encoder is ant making their rips. I have seen Brips at 300mb that are better quality than DVDrips of 2GB, because a better souce file was used by a better encoder, not because of the video file type that was used.
Hope that makes some sense??