I'd say, go for the first (the left) one.
It has the relaxed feeling that is associated with Papa Nurgle.
The other one might look more dynamic but the pose is not convincing, and the clumsy blade attachments aren't either.
I second that, go with the first (left hand side) model.
It brings a little more focus to the rib cage which frames the character nicely - an aspect that is lacking in the right hand one. It also looks like it allows a little more use-able space on either side of the guy, in which you can put in some embellishments: corpses, nurglings, pustulence - whatever you fancy to make him truly grotesque