None of them, Razer keyboards below the Blackwidow are pretty bad (I got burned bad buying the Lycosa), and there are better mechanicals than the Blackwidow.
But yeah, mechanical keyboards in general. First, figure out which (Cherry MX) switch is best for your usage scenario.http://www.cmuniversity.net/switches.php?lang=en
In a nutshell
Blues - Have a pronounced actuation point (which clicks as well, making it the loudest switch). Considered best for typing.
Brown - bit stiffer than Blue, same actuation point but doesnt click. Considered the best all-round switch
Red - Linear key in that the actuation point isnt pronounced, no click. Considered best for gaming as you can get fastest keypresses.
Black - TBH, dont know why one would get Blacks.
Green - Heaviest switch by a fair margin. Get this if you have meaty hands.
Do note that Khail, Topre are different switches entirely (still considered mechanical) and the above doesnt work. Recent Razer keyboards use their own switches (which are pretty much cherry clones, but different colours).