A 150 mm lens is always a 150 lens. So there is absolutely no difference between an MF 150 lens and an APS-C 150 lens. They will give identical, crop, FOV, DoF or whatever abbreviation on a given sensor.
One difference is that an MF lens has a larger image circle, so if you used it with a shift adapter you could do a lot more shifting.
Another difference may be that a lens built for a small sensor with very small pixels may be better corrected than a lens that is optimized for a larger sensor with larger pixels or film. Your 645D has 5.93 micron pixel pitch (distance between centers of two adjoint pixels), and the Nikon has 4.7 microns. So you need a piece better lens on the Nikon to achieve the same level of microcontrast.
i use a Sony A900 with Minolta/Sony/Zeiss lenses. I also have an NEX7 that I use an adpter and full frame A900 lenses. Because of the smaller sensor, and laarger image circle of the full frame lenses, ther is a "crop factor" of 1.5. Here is my question: I also use a Pentax 645D, and have several beautiful long lenses, such as the manual focus 150, 200, 300, and 1.4x ( matched for the 300 only). These lenses all have aaperature rings, and there is an adapter ring to attach these lenses to Nikon FF. Since the 645 lenses weere designed for a medium format image circle, i would assume there is also a crop factor when used on 35mm FF? What would that crop factor be?I preordered a D800E, and purchased a 14-24 Nikkor, and 18mm Zeiss ZF.2, but nothing on the long end which I only seldom use, so the inconvenience of an adapter would not be too big a deal.
Thanks in advance
Dave in NJ