Hopefully not running contra to the discussion, I followed those who put in 123 and was very close to getting one after some jackass mechanic I put my car with because I didn't have time to sort a dizzy problem cracked the dizzy housing. However, Cees came to my rescue and very kindly sent me a new housing. I 'rebuilt' (=took apart, cleaned, replaced some bits, put back together) my 051 dizzy and all is well. I did quite a bit of research on the 123, and spoke to the guys in Wimbledon, London (Southern Carbs, not the Wombles; they don't drive) who seem to be the closest stockist in the UK. In all, I couldn't find anyone who had anything but praise for the 123 unit. There are some confusing discussions on this site about springs and whether things need to be modded or not; people can't seem to agree about that, but it's minor stuff. If Cees hadn't come to my rescue and taken away my lame excuse to buy one at the same time as a new housing I'd probably have one now (I know that makes little sense, btw).
That said, yesterday I finished servicing my car. Naj and I changed the oil, brake fluid, did the values and all that other stuff last month but never got around to doing the dwell, points, timing, etc. I did all that yesterday. I was surprised that after a year and admittedly only a few thousand miles and a year or so, the dwell was spot on at 38 deg and the timing was barely off at all. I played around with it a little, of course, but it needed little. I then took it for a long (very boring) high speed run (for me 80 mph is high speed) as part of my winter lay up plan. Anyway, my point - if there is one - is that I like having points; my car seems to like them, too. If my dizzy does go one day, then I will opt for the 123, but I think I'd miss playing with a timing light, dwell meter, and tachometer. They're fun tools to play with.
Sorry, Hauser, that doesn't help much!
JH