EC145: No fadec but does not take much longer then the EC135 to start once you get handy with it and a feel for the "rigging" of the fuel control. Either aircraft I can get of the ground in less then 4 min, just the 135 a little less effort.
30-35 Celsius and up: The air conditioning in the EC135 is reasonable to bad especially compared to a BK117 or AS350, the EC145 is 10 times (if not 20 times) worse, and I have flown multiple tail nrs for hundreds of hours so I don't find this aircraft specific or type specific. (Metro and AMC completions)
The heater in the EC135 is good! The heater in the EC145 is as bad as the AC and flights over 45 min in the winter will result in loss of feeling in your feet. Good thing the pedals of the EC145 are tied into the autopilot, lol.
Moving the cyclic once on the ground in the EC145 will guaranteed get you in trouble if too enthusiastic in terms of Mast moment limits and a lot of maintenance to be performed, please, don't.
Behavior in turbulence: EC135, a lot of nose pitching up and down, rotor always steady even up to 75 kts of wind over the mountains. (even when I am far from "steady) Fadec does a great job, autopilot will "lose" it sometimes and need some assistance in "getting back". EC145, more of a shaking left and right, rotor all over the place and manual mode recommended for a reason. Autopilot seems to keep up better although I have not had a chance to fly her to the "limits" yet. So far she never kicked off on me.
How I would describe the difference? The EC135 is a BMW 3 series, the EC145 is a VW van. Both nice but different. For police work or even EMS (especially scene's) give me an 135 (2 or 2+) anytime. For Hauling 3 medcrews and an isolette, the 145 is the perfect machine.
Other then that they are both a dream to fly and designed to be single pilot IFR. And they are good at it! I have close to 1500 hrs in the 2 combined and am in love ! Remember, Just like a woman, no such thing as perfection....you just have to get to know her and find what she likes and what she doesn't like and sometimes there is no logic behind it, at least not for a simple mind like myself.
My 2 cents....