Gill,
I think this is a valid debate but seems to be going abit circular and in danger of
IMVHO.
I said it previously but over analysis is almost as dangerous as no analysis!
The numbers of rebreathers in total make statistical analysis dodgy at best, the lack of MCCR incidents could be pure chance.
I really think you ought to choose a unit that you are happy with, happy to service, setup, prep, drive, to fault find on and importantly happy with the manufacturers service.
Your subsequent diving of the unit will define its safety. (IMVHO as usual)
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Know your PPO2, Pre-breath, Use checklists, Validate cells at 6mtrs, Use pure O2 at or near surface, Use a BOV, Don't dive Solo, Change Slime and Cells as recommended by Manufacturer and RTFM!
Beware Fridge Suck!
www.hugsac.org.uk