Can some one please point out the difference between the two lenses. Which is suitable for which type of photography, which is better etc..

I have a canon 400d camera.

Cheers

From what I have heard, the 90-300 USM is alright, focuses fairly quickly, but the quality drops off at the telephoto end. Not that useful for low-light shots.

The Tamron 55-200mm f/4-5.6 LD Macro Di ll is quite a good lens for the money.

Either would be a reasonable addition to a kit lens, for example, for expanding your coverage out for wildlife shots or similar.

i bought the tamron , 2 reasons
it was only £80 and i already had a sigma that went to 300mm.the tamron does reduce the number of lenses i need to carry.
18-55 and 55-200 usually these days.

whereas prior to that i had 18-55 , then one to cover the 55to 90mm and then the 90 - 300 and i always took them all.

I had a Canon 90-300 and at was not sharp at the telephoto end, even when used on a tripod. They are cheap though in lens terms so good value for money. The Tamron will still have a good range as you are using it on a Digtial SLR, you might find it gives better results because it does not go up to 300.

Thanks to all for your feedback

Is it worth buying the canon 90-300mm if I already have the tamron lense?
(it came in bundled with camera but only just got hold of it)

It depends entirely on what you want to photograph,
If 200mm gets you close enough, then no. Don't forget you can
always enlarge areas of your pic on the computer.
Dave..

The Tamron is exceptional quality, I've been most pleased with mine. The low-points are the plastic/alloy mix for the bayonet ring.