The 135 and the 145 have similar avionic fits so that makes transition between them more easy within the new training fleet. Also, I believe, their avionics is far more like newer mil types too. (I imagine this might avoid the shock of moving from, say, gazelle to merlin avionic standards)
There are Slope handling differences on the 145 - but that is just another type's quirks, right?
If it's any help, I was a crew-chief for a few years and I had just the same type of arguments some years ago when moving from 355's to 145's. You probably wouldn't like what was told to the operators then!