Too soon for me to tell if my ML50's and 300's will be as durable as my 1990's Mag's.
I'd speculate the C size is more tank proof than the D size due to the laws of physics making a narrower tube of same thickness as a larger diameter tube.
But the way the ML25 is constructed is definitely going to be less prone to stop working because of switch failure. It's minimag/solitaire simple with a sliding contact that is forced closed by tension of the spring and circuit is broken when tension is released.
I keep the tailcap slightly rotated loose on my ML25's. Partly because I found a beam I like and leave it there. Then break contact via tailcap. If rotated loose just right you can momentary signal with it too. 18 hour runtime on the 3 cell version aint no joke either.
To me the ML25 series was the most dependable Maglite since the 1979 original, then the 1984 minimag.
With the electronic switches, breaking contact via loosening the tailcap turns the light off at the switch. You have to turn it back on via the switch. Great for stopping parasitic drain, but makes it not possible to signal like the classic Maglites could.
Some sizes for reference.
A 2xaa, a 2c BoyScout light from the 70's, a 1 setting 2x 123 light, a 2cell ML50 and both sizes of the ML25.
That's a Stinger anti-roll device on the 3 cell ML25 btw.