Is it your first command? If so I would certainly stay on the bus.
It's only several months longer to wait and by the sounds of it the more desirable fleet.
If I had flown both types I'm sure I would have more to add, but to throw in a new type rating, procedures, route structure AND an initial command all for the sake of not waiting until the new year? No thanks. If I was honest with myself in that scenario I would also want to assess the training environment where you are to avoid scrubbing out completely while taking too much on. There was a reason they used to have the 300 hour right seat requirement, and I'm sure that hasn't been cancelled to do a revolution in the training syllabus.
Command certainly trumps FO long term, but we are talking a matter of months.