Which one is better to use ?

Im not sure about iptables but it seems that there is a little problem with it.

I keep on receiving mails saying :
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/etc/cron.hourly/portflush:

iptables: No chain/target/match by that name
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any idea how to overcome this?

I think portflush is actually used by ipchains and iptables won't need that.

I think this is part of Port Sentry, which installs a cron to flush any firewall rules. The idea is supposed to be that Port Sentry listens on all ports, and a firewall shouldn't be used with it.

I personally don't care for Port Sentry, but if you use it, and you don't have a firewall configured, just remove the cron (delete /etc/cron.hourly/portflush).