E70 from year to year has various forms of the same component. Each year the form is changed to reflect fixes, hence the last year it should be much more reliable then say the first year. The f15 is a whole new platform and has the latest in BMW engineering so it has new tech vs the e70's old tech.
Old tech will always be more reliable then the cutting edge of technology. The principle behind this is that, the technology that is dated will have been tested significantly more than say something that just came out, since the real world is not a simulation. These real world experiences would provide problem-fixes and updates on the same component.
This is evident in anything these days, from iPhones, tvs, your watch, or say a brand new car.
That's not to say that there will be cases where you'll have reliable tech. However reliabilty statistics are aimed at answering how reliable the majority of vehicles are in the subset, not the individual members of the subset.
If you value a reliable driving experience buy an economy car they'll serve your purpose well
If you value anything above that then get what you want and be prepared to pay for that enhanced experience.
Reliability in luxury cars ain't nothing but a chicken wing!
BMW and Mercedes Build Beta Products!
Lexus build Release Candidate Products!
Why does this matter?
CAUSE EVERY TIME someone says Lexus has better build quality, one should consider what Toyota their Lexus Engine and chassis platform comes out of and how long that part has been tested in the real world!