I would have been happier with the 180mm lens, but I am not motivated to buy the 180mm and sell the 150mm.
I wouldn't be either. Actually, I got my 180 by mistake. In the late 90s, I ordered a second 150 as a backup from Calumet in Chicago. They didn't have one at the time and sent me a 180 instead, even though it was more expensive. After using it, I wasn't complaining and kept it. Nevertheless, it turned out that sometimes it was too sharp and clinical for the jobbut for those cases, I still have the 150,which is plenty sharp but a bit more forgiving for female portraits.