I would say ubuntu and it's derivatives :) as Mark pointed out .... it should be easy for devs.
We can go for personal taste and rolling releases etc, but it's not as fixed to stability and open-source as debian so you stay up to date and you get things like firefox instead of icefox etc ...
It's the mac of linux-distros so to say ;) .... one advice I can give is .... wait ~ 2 months before doing the dist upgrades :) .... so the biggest kinks are fixed.
Although as an advanced linux user I recommend trying out different distros :) ... I am an arch user.