The 840 and 840 evo are built with tlc nand, of which they say have +/- 1000 program/erase cycles. Most other drives are using mlc nand chips which are capable of 3000 -5000 p/e cycles. Intel's drives usually have 5000 p/e cycles and are more expensive, (and have the Intel name, and fame, which isn't cheap either) .
the Samsung 850 pro is looking very interesting.
If you fill 50% of your ssd with data which isn't changed a lot (operating system, programs) all the writing of the frequently changed files will be on 50% of the drive, wearing out those remaining nand chips even faster. Depending on the intended use, reliability can be an thing to look in to or not.
This may alter your perceptions. Hardware.info 840 EVO torture test
Our previous calculations of the lifespan of TLC-based SSDs were clearly off the mark. We made the erroneous assumption that static data remains in the same location on an SSD. We had put 160 GB of static data on the SSDs. Considering how much data was written to the SSDs in two and a half months, the static data was moved by the controller to other memory cells at regular intervals in order to keep an even load on all cells within the SSDs. That means that a nearly full SSD performs more operations in the background in order to move that static data around. However, that does not have a negative impact on the lifespan of the SSD. There's no difference between an almost full SSD and an almost empty SSD in that regard.
Even when you push an SSD to the max by downloading lots of movies everyday up to an average of 30 GiB per day, the SSD will still last you 24 years.
As often said in other threads, nearly any SSD made in the last year or two is fast enough for home use (unless you have some crazy high I/O demands or hunt in the bargain masement bin). Look for features (do you want on-board super cap for safe power down, built in OPAL level encryption), tools (like Samsung Magician), and in my case - how long has it been on the market without issues? Most issues being a screwed up memory controller chip/driver that causes data loss. So, I defer from suggesting newly released SSDs until they have a couple of months to be proven in the market.