Which SSH daemon should I use ?'

dropbear is more lightweight. The downside is that dropbear does not support that many features and is slower. OpenSSH does support the full set of features and is a bit quicker in the key handling. One set of tests found OpenSSH on the NSLU2 to be 8x faster than dropbear at scp transfers - 800kB/s vs 100kB/s (using "scp -c blowfish" as this should be the least CPU-intensive cypher).

dropbear is the default. To switch to OpenSSH see http://www.nslu2-linux.org/wiki/HowTo/UseOpenSSHForRemoteAccess