XP :Outpost 4 versus Outpost 6/2009

I n lately retrialing Outpost on XP.
While using OP 4 i have the feeling of a lighter firewall than OP 6/2009.It really feels like a pure firewall to me and the desktop feels smoother.The leak protection is really basic.

Another strange thing is that after installing Colasoft trial i m observing that with both ARP smart filtering optioned ticked in both firewalls ,the ARP traffic is different.

With OP 4 i see only :
"Who is <ip my PC > Tell <ip gateway>"

With OP 6/2009 i see
"Who is <ip my PC > Tell <ip gateway>"
and 2 of this
"<ip my PC > at <my PC MAC>

This means that with OP 6 i m ARP spoofable ?