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The 14" screen would be the killer for me, too small for 1600x900. You need to be up on the latest reliability results for SSD though if you go for the W530. There's some rubbish out there although hopefully not in a Lenovo. I nearly bought a ThinkPad of very similar spec 18 months ago but went for the Asus N53S instead, my 500GB Data partition is nowhere near half full despite me being a complete open source magpie so I wouldn't worry about 256GB unless you're planning on forking Chromium
"The secret of happiness is freedom, and the secret of freedom, courage."
Thucydides (B.C. 460-400)
Are you going to run any wirtual machines? If you are, you're probably going to have at least one virtual Windows Server - so ram will be an issue.
How about database servers? I have both Oracle and Sql server installed - so the 8GB memory I currently have is far too little, Visual Studio alone uses more than 600MB - so I guess I would go for the 16GB machine - I guess it comes with a DVD player that can be thrown out in favour of an extra harddisk ...
Independent of the screen size issue: More RAM, and SSD.
The RAM might eat the SSD battery life extension, but you still end up with more RAM and a harder-to-kill-mechanically disk.
It's a SSD, so dock & backup frequently, which also gives you a chance to deal with the limited size.