As I’ve mentioned elsewhere, I’ve fitted a few 123s. I like them.
The downside of the 123 (and other electronic upgrades) is that when they fail they tend to fail 100%. If something goes wrong with a points distributor you can usually manage to get home with a bit of tinkering, and if you carry a spare set of points and a condensor you can almost certainly get home - with a 123 or a Pertronix if they fail, then your tinkering is limited to calling for a flatbed.
A “spare” 123 is pretty expensive (unless you have a fleet of Jags to spread the cost), but for a longish trip carrying your old distributer (tested and known to work) is an option.