As you have probably realised you are getting differing advice based on each individual posters experiences and, I think, based on their age and position at the moment.
Snooky says that those who go for the command are,"usually a pain in the neck", well a very sweeping statement that means that at least 50% of the people Snooky flies with are a pain in the neck!
Don't pin too much on future expansion of aviation either, it doesn't always happen on
your doorstep and there are far too many variable that can effect it.
Picture this scenario, an interview panel looking for jet qualified F/Os, (very rare they look for captains), in front of you an F/O with a stack of longhaul experience and an ex captain with hundreds of short haul sectors all in command, who would you choose, the guy who is a proven F/O or the guy who is a proven captain and may well fit into the companies future plans?
Better to get your command course out of the way now than wait eight to ten years when you will be that much older.