Hi Guys,
When I started this thread it did not expect it to get so much attention. Thanks for your views, you are helping to clarify my thoughts. Most of the points made had already occurred to me but hearing them from others, with perhaps a slightly different twist, allows me to put my thoughts in perspective. Please keep your views coming in, It seems that I am not the only person interested in this comparison.
I have still not come to a conclusion. Much will depend upon the prices once the novelty value of these new models eases. Hopefully discounts will appear in a few months. In the past I have bought Sigma lenses for Canon at Orient Photo and have been happy with their prices and service. However since studying the prices in the Canon Forum I now realise that the place for me to buy to get best prices is Bangkok. (HK might be cheaper, but it's more hassle to go there). I have to admit that ClubSnap is my best source of info. on camera trends & personal assessments, thanks
A number of the comments have made the point that Nikon & Canon are by far the favourites of professionals, and by implication the best. While this may be true, one must bear in mind that the Sony A900 has not been available until now. I think this particular camera could shake up the market in a big way.
Someone commented that for such cameras that you need top quality lenses. One very good comparison of FF v 1.6 sensors said the opposite. The guy claimed that an old ordinary lens on a FF camera does noticeably better than a very good lens on reduced sensor camera.
http://www.kenrockwell.com/tech/full-frame-advantage.htm . On this basis I might be able to produce very good results using cheap second hand Minolta lenses. Combined with the A900 body being cheaper than 5D MkII it could be a very cost effective high performance system. I am unfamiliar with Minolta lenses so I'd be delighted to hear any comments on this aspect.
Over the past few months most of my photography has been panorama photography,
http://www.peterloud.co.uk/photos/SEAsia_07-08/Singapore_panos.html
(my apologies if you've seen them before), using an Sigma 8mm or the 10-20mm lens on a 350D. So I am much more interested in ultra-wide & fisheye lenses than long lenses.
Many of my panos are taken inside buildings which can be quite dark, on this point the 5D MkII with very low noise has a great advantage, but I normally do not go beyond ISO 800.
After some of the comments I am feeling that the A900 image stabilisation is a very important benefit. I like to think that I can hold my camera quite steady but now that I use a tripod for almost everything and can examine images at pixel level of detail I find I'm not as good as I thought :-(
Keep your comments coming, Thanks,
Pete