The DCR PC120 has a better CCD chip (1.5 megapixels compared to 1.0 on the PC105 model) The DCR-PC120 comes with every gadget you can think of. I have the previous model PC110E but because I use a PC to edit I don't use the built in effects etc.
you can't go wrong at 600 notes, I paid almost 3 times that for mine! It is a very nice camera. The limitations I have found are that because it has a small aperture it is useless in low light conditions. Mine doesn't have slow shutter speeds either which would be useful. If I was buying again I'd save a bit more and get a DCR-TRV950 3CCD semi-pro camcorder which is only a few hundred quid more than the DCR-PC120.
Here's the DCR-PC120 spec from the Sony UK site:
http://products.sony.co.uk/productde...p?id=11_61_924
and the DCR-PC105 spec:
http://products.sony.co.uk/productde...?id=11_61_2734
hope this helps,
Owen