This one's going to be easy because the results really do speak for themselves. Simply put, the RealSSD C300 turned in one of the finest all-around performances we've witnessed from a solid-state drive. We're used to seeing SSDs post impressive scores in some tests but deliver sub-par or even horrendous results in others. After going over page after page of benchmark data, though, I'm hard pressed to find a definitive weakness in the C300. The drive's random-write performance with smaller transfer sizes isn't particularly inspiring, and the RealSSD falls victim to a couple of the same FC-Test file sets that create problems for other SSDs, but that's really it. Otherwise, the C300 is a monster, often leading its rivals and rarely far behind them when it's not.
I would, however, avoid using Marvell's 6Gbps 9128 controller. The C300 is plenty fast on the 3Gbps SATA controller in Intel's P55 chipset, so you don't really need the next-gen interface. Plus, the Marvell controller gives up a lot of write performance. I have doubts about whether it's treating the TRIM command properly. The RealSSD may fare better when connected to the 6Gbps SATA controller built into AMD's SB850 south bridge.
All the fuss over faster interfaces takes away from what might be the most important ingredient to the RealSSD's success: support for second-gen ONFI flash. I expect we'll see similar flash technology in drives based on the next generation of controllers from the likes of Indilinx, Intel, SandForce, and others. For now, Crucial appears to be the only game in town, and the RealSSD is making the most of that advantage.
Now I will concede that the 256GB model's $610 street price is a rather onerous pill to swallow, even if the associated cost per gigabyte compares quite favorably to other SSDs. Budget-minded folks will probably want to consider the 128GB variant, which sells for a less imposing $374, albeit with a slightly higher cost per gigabyte. That 128GB drive will be slower with writes and random reads, but I'd expect it to remain competitive overall. It should be just as fast as the 256GB model with sequential reads.
I could try to extrapolate the 128GB model's performance based on Crucial's lower performance ratings for the drive, but I'd be hesitant to make a recommendation without seeing how it fares in the real world. The 256GB model has certainly done enough to earn itself our Editor's Choice award, though. The C300 offers the best all-around performance we've seen from any consumer-grade SSD, and it does so at a competitive cost per gigabyte. If that's not Editor's Choice material, I don't know what is.