Motion might be ok for small comps but its not a hard core comp package even with conduit. Motion also lacks A LOT of the higher end tools you are going to need like real keyers. The keyers in Motion are horrible and it doesn’t easily allow for doing channel op type keys. So unless you think a Key is just dropping in a single keyer motion isn’t going to do the job. Its hard to do compound channels and such in motion that are still hard in AE but at least it does them. If you are going to be doing real commercial or film comping you really should look at Fusion or Nuke. Also there are some pretty basic tools missing from motion like either a spline or grid warper. fusion and Nuke will allow you to read in real 3d geo and cameras for doing projections on to actually 3d geo. Motion is fine for basic animation and basic comping but its no high end tool and its can’t even do some basic things shake can do. It just depends on if you are really comping or just layering files.