Chris

The differences between electric showers really are their power consumption and cost of spare parts. Higher power consumption basically means better water flow at any given temperature. Cost of spares is self explanatory. I guess you can add to that, how often you’re likely to need spares.

Sadly I can’t offer you any specific insight into Mira or Triton units, however I can caution you against making generalisations - I have two Gainsborough units in my house (the brand is now owned by Aqualisa) and one of them hasn’t needed anything doing to it in 20 years while the other one has had its guts replaced 3 times. They aren’t the same model, which tends to suggest some of their designs are weaker than others.