Nope. Your OS vendor already did the work to make both versions of IP work. And as I mentioned, if you're using a decent firewall you can write IP-version-agnostic rules just as easily as you can ones that depend on the version.

Plus, most SOHO firewalls default to dropping unsolicited non-ICMP traffic. That's the exact same security stance that IPv4 + NAT gives you. You have to go out of your way (or be using fancy gear that is aimed at people who know what they're doing) to expose your LAN hosts.