B47 engine appeared in the F10 in June 2014 (as I have one). It only appeared in the F30 from 2015 with the facelift.

Regarding which car to go for, the F10 is a much longer/wider and heavier car than the F30 so take that into account as the F10 can be awkward or cumbersome enough to fit into car park spaces especially tight multi-story car parks. The 2.0 litre engine whether it be the N47 or B47 is ok in the F10 but much more suited to the more nimble F30. However the F10 being from the class above the F30, so has better standard equipment and is more refined while the smaller lighter F30 handles and performs better in x20d form. One thing I would recommend though is that you go automatic. The ZF 8 speed automatic gearbox is excellent and is a perfect match to the oil burner.