As you appear to be looking for a second hand Morgan and not specifying your own build, I would keep an open mind and go with the car that most appeals to you aesthetically and has the right level of specification that will facilitate your driving pleasure and style. Both models are fast enough to get you into trouble, as well as create those magical halcyon moments when necessary. If you rarely drive in the wet (not something I do by design or choice in a Morgan) then the Plus six with care I'm sure is addictive coupled with an auto box to take the strain out of congestion traffic.
The car has to physically appeal to me in the first place, like one of those moments when you eg come across a bevy of Morgans, you may find you naturally gravitate to one or 2 cars whose colour and spec makes you slightly envious and you linger longer around those cars...those are usually the ones for me. The model specific idiosyncratic features hopefully you can iron out over time.
I never keep a car that I start to lose confidence in and cannot rely upon, life's too short to spend it in garages resolving the same or similar problems. Wires are a great static display attribute sparling in the sun, but maybe not as much fun going down an undulating rough road, compared to alloys
