I had a Series 3 OTS and while I loved it, I sold it and bought a Series 1 coupe, which I like even more. I owned the Series 3 for 10 years, at which time it became a 100 point car (actually, 99.4. Never had a problem with it at all.
If you want a 4.2, get the Series 1. Their value has increased significantly over the past two years and the gap between convertables and coupes has shrunk considerably. I perfect restored Series 1 coupe is now north of $100k.