To put it simply, WEB-DLs is paid content from iTunes with superior quality in all areas. Networks release them on a flat rate of $2.99 on the US iTunes Store, £2.49 in the UK iTunes Store and $3.49 in the Canadian iTunes Store. The content comes mainly from HDBits but there are also other trackers who have minor internal groups who work on releasing these to the world.
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BDRip comes directly from the Blu-ray source, while a BRRip is encoded from a pre-release