154CM>S30V>M390>M4=S90V, but this isn't to say any of them are bad... I just have my preferences.
I use the crap out of my knives, so ease of sharpening is a big decider on my hierarchy.
Benchmade's 154CM is pretty tough, easy to sharpen, but the biggest pro: It takes an absolutely astounding edge and holds it forever. I can consistently get my 154CM blades to dropcut hair using only diamonds (no strop). When I want to show someone what a truly sharp knife is, I grab my 3550 or 9051. Both are set at 16º/side and are kept slightly better than "three-finger sticky".
S30V is just a consistently good steel that is "easier" to sharpen than it's more high-tech brothers. I can get it pretty dang sharp, but it doesn't seem to like holding the freaky edge for too long. It also chips faster than 154CM, so I run these at 16º with a 20º microbevel.
M390 takes a scary edge, but chips at smaller bevel angles (<20º). Those chips are an absolute pain to remove, and as such, I've never kept an M390 Benchmade around for too long.
I can't seem to get Benchmade's M4 to take a scary edge, but that could be the bloated blade geometry of the Contego and the 20º bevel I run for harder tasks. Conversely, Spyderco's M4 is terrifying when sharpened on diamonds. BM's S90V can get slightly more "crisp" than M4, especially at 16º. Both steels hold a working edge for a shocking amount of time, but require a solid afternoon on diamonds and strops to get back to a fresh edge (especially S90V). Sharpening S90V is actually my least favorite thing to do to/with a knife, and usually resort to a small microbevel just to speed up the process.