With both Samsung and Intel you're talking top-of-the-food-chain devices.
Comparing the 535 to the 850 Pro isn't particularly fair since the 535 is a value oriented drive. The primary advantage there is that the 535 is *cheap*!!! I picked up a dozen for around $150/each back around Black Friday. The lowest price for the 850 Pro was around $210.
The problem is that the extra cost probably isn't justifiable. The way the warranty on these things work, the Samsung is 150 TBW (terabytes written). So if I take 150000 and divide by ten years and divide by 365 days, Samsung is warranting the drive for 41GB/day for ten years. The Intel 535 is 40GB/day for five years. I can make that work nicely for the Samsung by specifying an expected service lifetime of five years (or less) at which point the 535 is still only rated for 40GB/day but the Samy becomes 82GB/day.
So the thing is that in the last five years, we've gone from SSD's being around $2/GB for bottom-tier SSD, to today where it is 31c/GB for good-quality or
21c/GB for cheap stuff. And the real question is, would I be RMA'ing a dead SSD, or more likely just buying a replacement, at a lower cost/GB?
I was looking for a hypervisor solution too. But since they're going to sit in a data center 800 miles and 14 hours away, everything's paranoid-redundant. Both chassis have a nice LSI 3108 RAID controller in it. The RAID controller has 3 1TB WD Red drives, two in mirror with a spare, for high endurance operations like logging. There are then two mirror sets of Intel 535, with a spare, making a total of eight drives per chassis.
The problem is that I hate hypervisors because they give you all the information except the stuff you really want to know. For that you've got to dig into the CLI. But when I do so, it seems like I'm even managing to live within the 40GB/day budget. Yay!
But I do expect that the drives may not live out their lifetimes, at which point I probably don't really care if they're under warranty anymore, because by that time the Intel 555's will be out with a 1TB drive for $99 and 400GB/day endurance.
My vote? Probably get the cheap-but-reliable.