At the moment i have a nikon d3000 and would like to upgrade it,so at the moment i am looking at a D5100 or D90
Am a little unsure what to do at the moment but at this time the D90is my choice i know that it only has 12.3 megapixels and the D5100 has 16.2 megapixels but the D90 is winning i am not too worried about megapixels as i dont print any bigger than A4 size to be honest,Could you please give me some advice and pro's and con's
I would sujest you look to the future and look at what you want to do in 5 - 10 years time with your photography. As i see it at this point one is as good as the next and bugit may make your choice for you.
The D5100 has a few things going for it over the D90 - the articulatied screen, and the sensor with more pixels, better dynamic range and higher ISO ability. It probably has better video, too, if that's of interest. Most of the other differences go the D90's way. There's the second command dial, the top LCD, bigger & better pentaprism (vs. pentamirror) viewfinder., and the focus motor for AF lenses. It's a tough call.
If you sway towards the D5100, it's probably worth looking at the D3200 too. I don't think there's much between them apart from the swivel screen and newer sensor.
Similarly, the D7000 is probably worth considering, but given that the D90 can be had for £350 less at WEX it's a big ask. The D90 looks a bit of a bargain; I wouldn't want to be trying to sell a secondhand one at the moment.