As an owner of an original BG250 with the 15 inch speaker, I would go for the 112. I have gigged it loads and it is loud enough for any pub gigs. As it has the same output as the 15, although a smaller speaker, it should cope ok. The 15 weighs 16kg and is ultra portable, so the 12 won`t weigh any more. The speaker will be a 4ohm one so you are getting full power and that is why there is no speaker out option.
It is also great for plugging in the phones and computer for silent practice. My advice, buy the 12 and sell the external cab.