How does the safety record of the twin piston Diamond DA-42 compare to the single piston DA-40?
So it appears that Diamond answered this question for me. 

See this page:
http://www.diamondaircraft.com/about-diamond/safety-features/



From this chart, it would appear that the DA42 has a slightly higher accident rate, and of those accidents, even more are fatal (which makes sense due to the higher speeds). Still loads safer that the SR22 though, and I'd personally prefer the 42 over water as well.