CIPE vs IPSec

I have a VPN on 4 firewall based on Linux RedHat7.1 (kernel 2.2.x) and Cipe (ipchains) to connect 4 network. Someone told me that I have to upgrade OS to Linux RH7.3 (kernel 2.4.x) and upgrade the VPN to Netfilter-Iptables to upgrade to the standardIPSec. I tried to find something to clear my ideas, but I haven’t found nothing that explain a clear match of both technologies.
Any suggestion? I will upgrade my systems only if there is the real need to do.
Thank You.
Andy