"Bond don't rate the Explorer as it is unreliable, "a good idea cheaply done" is what they said to me"
A completely unbiased opinion!
As for unreliable, in the past couple of years in flying both the 135 and the 902 most of my downtime has been at 135 units.
Personally I think there is little to choose between the two for downtime. I find the 902 a better HEMS platform (the best by far for UK-style HEMS ops) and certainly scores on AEO performance compared to the EC135T2. I can't comment on the T2+ as I haven't flown it. (The T1 was a great police machine bit it's being floored for night ops by regulation!)