The problem I had is my Android phone was very unreliable with IPv6 enabled on my network, it would constantly claim no connection or just take ages to do anything
Also I have all my clients set with static IP addresses but the Xbox One would change its UUID every time its rebooted. That meant I would have connectivity issues every time because I had specific firewall rules to only open incoming connections to specific clients.
Then there is the fact I monitor bandwidth use on my LAN, there doesn't seem to be a facility to do that on IPv6 on pfSense.
So at the end of the day the only choice I had for reliability was to stick with IPv4.