Haven't had one, but do understand that the crossflow head creates access issues for the ignition. I would suggest posting up your issue and questions on MG Experience, as there are a lot of experts that can advise and are running the crossflow head. If you want to start a big debate, all you need to do is mention Pertronix versus points. I have been running a Pertronix unit in my TR6 and it's been flawless. If the distributor is in good condition, I would think replacing the points every couple of years shouldn't be that bad. I would guess the carb removal would only be required if you need to pull the distributor.
I have had a Pertronix set up in my TR6 for many years without failure, but one that was in my Morgan suffered from infant mortality. The Pertronix in my MGB GT has been reliable, so my answer would be, give the Pertronix another chance, but do what I do--always have a set of points in the glove box of each car as a back up.