Closing for migration is a bit tough. Right now, if you don't want to send the post to SU or meta, you have to move back up the close tree.
My suggestion is to add a manual "other" option to the off topic -> migration option.
Of course, the default is where it seems to be going right now, which is a generic "unclear what you're asking" path, which is simply the easiest, requiring nothing but a selection and no typing, but this doesn't feel right.
I'm not quite sure how the act of migrating actually interfaces with the close choice, but I think this is one of those small things that make review chores a bit more tedious for those who choose to do them. I find myself clicking skip more often, lately.