If I only shot B&W and I just wanted to get into medium format, I would get the mirror lock up version 67 with a plain prism and use a spot meter for determining exposures. For color slides, the 67II with the AE prism is a better choice.
I originally got the Pentax for the 6x7 format for black and white. I got into taking slides with it, as well as black and white, and ended up buying a 67II for that. Now, I use the 67, unmetered, for B&W and the 67II with the AE prism for slides. But, if I had to do with just one, I would go with the 67II and the AE meter prism with a 105mm and 200mm lens. I would have to think about the wide angle lens. I have a 45mm and I would want to try a 55mm. The 45mm is a little much, but I wonder if the 55mm would be wide enough. Also, I have heard the 55 is not as sharp as the 45mm. The later 45, 105 and 200mm lenses are all very sharp with good color and contrast.
That said, I have had a Hasselblad for a long time and I would not part with it. Its just that, today, at the entry level, I think the Pentax would be a better choice. Start with it and, later, if you need more, get into the Hasselblad system.