pfSense is truly the best if all you want is a firewall with more features.
I'm actually running in off a compact flash card inside a VM on an ESXi host (yes you read that right). I delegated 512 of ram, edited it to the "embedded" platform, and didn't install a swap partition. Runs like a champ on the flash card with nearly 0 writes.
I'm running appropriately 10 PCs on it, can jump up to 12-13 depending if I turn some more VMs on.
Just a note when originally searching for a firewall distro I found pfsense to be the only one capable of bridging a tapX interface with the physical lan connection. This can be used to created a bridged VPN.