My focus is definitely for time lapse and I have a little experience using papywizard for just that purpose. However, I found that using a software based control system was difficult in the field.
I agree with the computer in the field ! So if you focus mainly on timelapse, go ahead with MX2 so it'll control eventually your rail or motorised system to move camera, and it'll be able also to control the Merlin (just buy or build the communication cable) and you are done
My shop for panoramic photographs: http://magasin.skivr.com
Nodal Ninja 4 R-D16 on Benro Tripod + Ultimate R1 on Nodal Ninja P2 + Nikon D800 + Nikkor 10.5 + Nikkor 14/24 f/2.8 +Pentax 645D