I knew and loved the Dennis Dart quite well during my time with North Birmingham Busways, from a driving and maintenance point of view. Yes they had electronics, and a very basic computer (called "Aladin" - my engineering manager didn't like my inference that if you rubbed the headlamp a genie would appear and mend the bus!) but they were basic, reliable and had known faults you could be ready for. Any road vehicle you can't fix with a hammer, a screwdriver and a reel of fusewire is going to cripple your maintenance budget, I found!
The Daimler Fleetline was "alright" (said dispairingly!) once you were used to the steering that always wandered, the heavy right pedal from the Gardner engine and the mud-traps in the chassis rear end that held water long enough to induce terminal corrosion unless heavy mid-life reconstruction was done. Personally I preferred the Leyland AN68 Atlantean, which NBB used many of, sadly they were rare elsewhere in the midlands.
Leyland Nationals - yes, OK again, a driver's and passengers bus when new, but so heavy on rear barke linings - 6-8 weeks life was typical, whilst the front brakes would do 18-24 months before a reline was necessary. Once you were used to the roadholding that felt like a jelly on a wet plate (but they actually clung to the road like brown stuff to a shovel), they were OK. The nearest description I can find to them is that they handled like a speedboat - you felt you were almost in full control!