Ive just heard that the two mechs are hard wired and if the wires get damaged the whole mech needs replacing. Whereas with Di2 Shimano uses plug in wiring. This sounds like questionable design but is it a problem in real life?
The FD and the RD have a short "tail".
In the case of the FD, if the tail is damaged, yes, it's a new FD but you have to try pretty hard to damage the tail. Worst case is a spectacular chain drop but apart from that, it's hard to see how damage would occur in a properly assembled system.
In the case of the RD, if the "tail" is damaged, the actuator unit can be replaced - it's a SC only job (not one for your local Campagnolo ProShop even) as if you make a mess of it, it's an expensive mess and there are some very specific tools required to do it correctly, which even most shops don't run to - a 0.5 nm torque screwdriver, for instance. If, as someone-or-other's law dictates, your gear is not in a "helpful" gear when the damage is done, a lot of the RD has to come apart to get the actuator out and for that, a knowledge of the entrails of an EPS mech is pretty essential. There are lots of small parts that it is easy to lose (especially if you don't know they were are to start with) and none of them are routinely available as spares.
Again, though, in real life, you have to try quite hard to damage this cable section. The most common (maybe twice a year) is someone trapping the cable under the head of the rear QR.
The long cables attached permanently to the Power Unit are all internal to the frame so though they are the most vulnerable because of their length, once correctly installed, they are pretty safe from mechanical damage.
The interface cables are probably the most vulnerable - the one from the IF to the PU is OK, it has a connector inside the frame and again, with correct assembly, it's hard to see how it might be damaged. The two cables to either shifter, though, need correct routing and when doing jobs like re-fitting the bars to the stem after traveling with the bike in a bike bag, for instance, you need to check you haven't trapped either or both under the stem face-plate. We get a small number of those each year. Don't remove your 'bar tape with a blade and ensure that the cables run on the inner curve of the bar, that you leave a short loop under the bar tape and that you run the cables through the channel on the upper rear of the lever & through the cable trap in the lever body before plugging up and closing off the door into the lever. These precautions will protect the cable from damage when the levers are struck from the top or side, or if you crash and slide down the road, shaving the bar tape off the upper curve of the 'bars. In this respect, the advice given by both Shimano and Campagnolo is broadly similar, the mechanisms differ a little, that is all.
I have never seen (as I have with Shimano) a cable connection jerked out by a crash or hitting a pothole with the front wheel when riding on the hoods, due to the lever moving, nor problems with connectivity resulting from frequent opening and closing of the connectors (can happen with the Shimano Battery to Junction Box "A" lead).
As in most things in engineering, there are many ways to get to the same end-point. In this case, Campagnolo chose a simple wiring loom, thermally sealed in to most of the components, to remove the risk of water penetration (those who know a bit about the history of early experimental versions of EPS will know why), where Shimano went for a more complicated loom with more connectors but in their view, greater flexibility, making it possible to add extra shift options, for instance.
Campagnolo have software in two places only, which will always work at least as well as the oldest piece of software - Shimano chose a more complex path with Software in all 6 elecronic parts of the system, which broadly, need to match for version for the system to behave completely correctly ... again, a choice. Proof that TIAMTOWTDI (There Is Always More Than One Way To Do It) ...