BazC took the words out of my mouth. its key placement for ergonomics with silo. thats why it has the funny key sets.. i remember the keys by location, not by the key designation. wings3d is free, kind of hard to knock that. but for a hundred bones, silo offers a great tool set, that usually cost's about 10X as much, and all the hoopla about workflow in silo isnt all hype,its really pretty slick. like Teyon said, its a personal preference kind of thing, that and taking the time to become proficient with your tools.