Well I've used all 3, but I stopped using axxess when I moved to Screamer, and I stopped using Screamer when I moved to DC, so I can't really comment on how 2 of the 3 currently rate themselves.
But never had an issue with Axxess, the price tag was the only thing that made me move. Always available, always reliable.
My time that I was at Screamer (left them end of November), was horrendous, don't know if they have improved. I could not access one of my mail accounts, and had about 80% downtime in the 15 days I was with them.
On DC, its been a very very bumpy ride, December started good but went downhill, January was a good month, February was a nightmare speed wise, but so far March is purring like a kitten.
So I can honestly say, Axxess if you have the capital available, and DC if you don't, but the whole seacom connection is still shakey, so unfortunately it means there will be speedbumps on a DC connection, but as with all things it takes time an patience, and it does get better