Is it safe to run a webserver on 5.x ?

[bsdfsse]

I started running FreeBSD because a friend of mine is going to run a 
website on 4.10-STABLE.  Someone had told him that 4.x was "safer" to 
run than 5.x.

Recently I had a hardware problems on one of my machines that is forcing 
me to run 5.x on it, instead of 4.x.  Should I lobby my friend to also 
run 5.x ?  His webserver will be behind a hardware firewall.

Its my understanding servers on the web often run the "security 
release", which is RELEASE+fixes.  That way, no new features in STABLE 
introduce more exploitable bugs.  Other people run web servers on STABLE 
(they must feel confident that nothing new is going to break).

After reading different places on the web, I haven't been able to draw a 
conclusion.  Any suggestions?

Thx!