Live draft - No logic built in to pick by needs. I dont think you can prioritize what position to take in each round either. This is a problem if someone isnt available to draft. .
I just checked and you can only keep 16 players. You can do IDPs as well.
CBS is solid but expensive.
I took over as commish for our keeper league at CBS and moved it to ESPN. We are having a bunch of new owners so we are starting from scratch. I have our league set up for 18 roster spots. Also, from your "My Team" page you can rank your own players and here you can set how you want the auto draft to select your picks in the event your not there.
Last year was only my first year in fantasy so I only have CBS and what I've seen on ESPN to go by but IMO why pay $200 for what you can get for free. The potential winners of our league sure are happy about having an extra $200 going to the prize pool.