Basically my 480GB one,a mates 480GB one,someone I knew on a forum who had two 960GB models,and a relative who had two Ultra II models,had them fail or have an issue. All around one to two years old.
It could be a faulty batch,but looking online(and even people who had failed 480GB/960GB ones on here) it seems they have "sudden kaput" syndrome,where everything looks pefectly fine and the next time you boot up it just stops working. A mate who bought a 480GB at the same time as me,but rarely switches the PC off,still has a working drive.
Why it pissed me off soo much,is I had a hyper modded FO4 playthrough and had not backed up all the mods and saves fully to a secondary drive. Since one or two of the mods were removed from NMM by their authors it nearly wiped out a playthrough a few 100 hours long.
Hence,I refuse to touch an Ultra II drive,and will only get another Sandisk if I am certain it does not have this boot-up issue.
OFC,some other forum members had no issues,but I can only really go by my own experiences!!
OTH,the Crucial drives seem to be fine,and I have a Kingston SSD I won on Hexus in 2012 which still works fine now.
Hence I wouldn't go too low end for a drive,if its a few quid difference.
However,some of the Chinese 360GB drives are under £70 if you want a cheapo drive,but I cannot promise how reliable they are.