Which Better

Well, I would incline towards K550i, this being a model of Cybershot series, This has been one of the fantastic phones I used. Though it has a 2MP resolution, it seemed to be the maximum resolution given to the phones of the mid-range. The picture clarity has been quite good with the resolution given. The only disadvantage is that the Zoom feature isn't available when you take the pictures, however the same feature is available when you shoot the videos. This being a Cybershot model, they have designed to be a camera based mobile. The sound clarity is just fine and it goes up when you are using the headset provided. Certainly will cheer for K550.

both the cell phone of he sony ericsson you mentioned k550i and the sony ericsson m600i is cool phone but rather i will suggest you to go for a k550i as i have used it in my hands ... it is cool cell having 2.0 mega pixel camera and the awesome music quality both in head phone and the speaker..

I have one friend that uses the first one says that it's quite pratical and has many good utilities and stuff. But then again I have a friend that has the other one and says that it's more advances and has even more stuff. So well, stuff, you know. Hard to choose ;)