If you accept the fact that risk is a co-efficient of the number of things that can co wrong, probability of the events occuring and the impact of the events ...then I believe that rebreather diving is inherently more risky than recreation diving.
As we move into deep technical I believe that the risks start to equalise with there being a similar number of different potential issues. While I would be hesitant to state that rebreathers are less risky than technical OC, on balance, I am comfortable with the risk/benefit charateritics presented by rebreathers and do not enjoy diving OC as much as I used too (noisy and cold).
JMHO and more a statement of belief than anything else
Nick