the 180 as best overall versatile lens. That's the very first lens I ever got for my RB. I added the 90 later to give me something wider. I've not shot with the 150 SF but that's a bit of a specialty lens.
Depends on what type of portraits you are talking about. For tight head-and-shoulders stuff, the 180 W-N is the cheapest good lens in that length range, and it has nice bokeh. But I think the 210 APO and 250 APO are better, and better choices for that type of shot. For casual portraits, esp. with shallow DOF, the 110 is nice. For environmental portraits, I think the 65 L/A is hard to beat. Super sharp, wide but not too-wide.
“Photography is a complex and fluid medium, and its many factors are not applied in simple sequence. Rather, the process may be likened to the art of the juggler in keeping many balls in the air at one time!”
Ansel Adams, from the introduction to The Negative - The New Ansel Adams Photography Series / Book 2