The 120 came out pretty late in during the screw mount period and is a uncommon, collectible lens. I've never used one, so can't tell you anything about it, but did Asahi ever make a bad lens?
The 150's are pretty common, I see them on eBay a lot. The 150 is light, compact, slow, and sharp. For me it fills the gap between my Vivitar 90 and my 300 perfectly in my M42 kit. When space was at a premium, I've taken whole trips with a 35 and the 150 as my only 2 lenses.