Mature Belle has the same content as one finds on the fully reviewed Mature XXX Archive. That means that there is a healthy dose of non-exclusive main content as well as links to tons of extra stuff and bonuses.
MatureBelle has 199 galleries with photos ranging from softcore to hardcore sucking and fucking. Some of these pics are even high-res, although not all of them are bigger than regular-res. There are 200 full-length videos to download in good Windows Media format or mediocre iPod/PSP compatible MP4s. Three granny feeds provide more streaming mature action.
There are 59 bonuses listed but only about 50 bonus sites are unique. Even those have scenes that may overlap with the over 2500 galleries and 4000 diverse videos offered in additional sets on the main site. Overall, despite its non-exclusivity the quality is almost as good as the quantity so Mature Belle seems worthwhile.