It's actually hard to say. You might be very lucky, someone else might be very unlucky. Generally, RAID was 'invented' to operate on cheap, commodity hardware, where the failure rate might be high. When it comes to data, most reliable one you can find (mostly due to its probe size and lack of competitive reports of similar size) are Backblaze's drives reliability reports.

I've exclusively purchased WD drives - and most of them are green. I have ten 2TB drives and two 5TB drives. 0 failures.

However from the IRC channels I frequent - many people have had one or two die over the years. So I consider myself lucky.

I had a 1TB WD Green drive that failed. Also had another failure with 320GB USB WD Passport.

Probably just bad luck, but I don't feel like buying another WD drive.