Proftpd is definitely the better one. Follow the link for more info: http://howtoforge.com/forums/showthread.php?t=5210&highlight=vsftpd+ispconfig
I had a similar problem with proftpd hanging up. Set Code: DelayEngine off on proftpd.conf and see if the problem persists. This fixed the issue for me.
I solved it a month ago upgrading proftpd to 1.3.0 from sarge-backports. I suppose etch's proftpd will be free of this bug...
this fixed my problem. also I had the part after "sleep" commented out, so I enabled that too. now in logs I see: Dec 16 23:59:01 ProFTPD killed (signal 15) Dec 16 23:59:01 ProFTPD 1.3.2c standalone mode SHUTDOWN Dec 16 23:59:07 ProFTPD 1.3.2c (maint) (built Thu Nov 18 00:37:33 UTC 2010) standalone mode STARTUP thanks falko.