You're comparing apples to oranges if you compare mx and bx. If you say bx is prone to failure then why not compare to a drive in the same segment? Don't compare dram and dramless drives.bx series is more prone to failure due to low end controllers. MX series on other hand is a solid one. plus I have one for more than 4 years or so!
Also, your sample size of 1 mx ssd is hardly representative and not statistically significant. I've been using a bx as a boot drive for the same amount of time.