I use the Rotochamp projections because they are updated throughout spring training as roles and lineups change and free agents are signed. The other rating systems are static. One of the nice things about Rotochamp is the ability to tweak the projections yourself.
Projections are also updated by Roto Lab and are linked to the Baseball HQ service. When using projections it's important to keep in mind that the projected stats may not account for the idiosyncrasies of your league. For example in my home league a 5-category starting pitcher (we use Wins, Net Wins, ERA, WHIP, K's) routinely goes for $10-15less than a 5-category hitter. Makes little sense especially when you consider that we roster 9 pitchers and 12 hitters and therefore a 5-category pitcher has a greater impact on the categories. I like to compare projections and tweak the software as much as possible to confirm to our league standards. It would be helpful if you could access historical values for your league's past auctions to benchmark against.
I got a free 10 day trial from rotowire. I must say that I am not impressed with their draft software. In one of my leagues, keepers are tied to draft picks, and I could never find a way to properly enter the keepers for that league. Also, the software seemed to process changes (draft picks) very slowly.
I've been playing around with rotochamp for about 10 days now. It seems to work very well. I just hope their player projections don't steer me wrong.
I have used Fantistics for years and I do like it. It allow you to set it up with 20 some different cat's if you need to. It is easy to navigate through with the ability to lock keepers, changes values all pre-season and a very nice inflation factor throughout the auction process. In addition you can manually change any stats/projections that you want, thus you customize your own rankings. This is very important to me personally as I change the projections of roughly 100 players prior to the auction. It is based on-line, but only for updating projections, so at the draft you are off-line and no issues. Also, you can set your projected %'s you want to spend on bats and pitching and it will recalc based on the %'s you want to spend.
I have thought trying another for the hell of it, but I just keep coming back to Fantistics.