Predated: The phone I'm seriously looking at getting at the moment is the Sony Xperia Ray
http://www.gsmarena.com/sony_ericsson_xperia_ray-3972.php
It has a really nice screen (3.3inch 300ppi Vs the iphone 4s 3.5inch 300ppi), 8mp camera and isn't a giant phone ( the biggest plus in my book) , plus all the extras like dlna.
It also has cynoagen mod support which I like too.
The problem with the current 'Sony Ericsson' range (As I see it and from what I've read) is the GPU. It's an Adreno 205.
Plus, HSDPA max's at 7.2Mbps and no NFC.
And the Ray also has other considerations; the screen viewing angle could be better and no HDMI.
If none of the above are a problem, then the SE Ray is a good and quite cheap phone.
If you're comparing to The iPhone 4S then I'd look at the GPU and the screen size and then expand out from there.
Don't think the SE Ray comes anywhere close to an iPhone 4S on GPU.