I've worked with lots of (enterprisy) hard drives and SSDs. The hard drive failure rate was easily 10x the rate of the SSDs, but the SSDs basically never gave symptoms of impending doom. They just disappeared from the data channel. We did have one group of drives that gave symptoms... 50% of the batch dropped dead within 2 weeks of entering service, a good number failed over the time it took to get the rest of them replaced. And one drive that had very poor throughput for several minutes did show SMART metrics that it was reallocating sectors, but we took it as a sign of death and replaced it; I think it might have worked fine once it calmed down, but we'll never know.