V500 & V525 are the same phone (although  the V525 has a blue front, the
V500 a silver one), the different model numbers seem to be there to allow
both Orange (V500) and Vodafone (V525) to claim them as "exclusive" to their
networks. The V600 (currently availible on o2 & Orange) has an HS800
bluetooth headset included in the box, has a (IMHO) nicer keypad, offers
video playback, has a metal shell rather than plastic, the front and back
covers are interchangable and it has a circular light around the Motorola
badge on the front that flashes different colours to indicate different
phone status messages (blue for an active bluetooth connection, white for
charging and so on and can be set to flash different colours and colour
patterns for incoming calls from different categories of phone book
contacts. Be aware that all three have had their firmware buggered about
with to a certain extent so that none of them work exactly as discribed in
their respective Motorola manuals availible here...
http://direct.motorola.com/manuals/29129_410_eng.pdf?country=GBR for the
V600...
and here...
http://direct.motorola.com/manuals/29128_407_eng.pdf?country=GBR for the
V500...
and here...
http://direct.motorola.com/manuals/29177_409_eng.pdf?country=GBR for the
V525...
HTH