WordPress because it's extremely customizable and extendable. No one special tube script can beat WordPress with all these themes and plugins developed for it.
For example.
- Which exactly specialized tube script and process (parse) any free-formatted XML feed?
- Which exactly specialized tube script can automatically spin your video titles and descriptions and/or translate them to other languages?
- Which exactly specialized tube script allows to use any FLV/MP4 player by your choice?
- Which exactly specialized tube script can automatically post your video links among with descriptions to Twitter and similar social networks?
- Which exactly specialized tube script can automatically post your video thumbnails to adult pinboards like sex.com and similar?
There is a ton of other extremely useful things that you can easily do with WordPress-based tube but can't with specialized scripts. The WordPress engine is being maintained/extended by 1000's of people around the Globe, so it can't be beaten by any specialized script
