welcome to the IPFire community.
Choosing appropriate hardware for IPFire is a difficult task indeed. This wiki page gives some buying considerations; especially having active NICs is important.
That being said, if you are planning to use IPFire’s IPS (see here for configuration recommendations), I am afraid both boards won’t make you happy. It depends on the bandwidth you want to have available behind your IPFire machine, but in general, the current landscape of ARM SBCs does not really fit more advanced needs.
Some people use supported ARM boards as a “firewall in the pocket”, but they are merely using IPFire’s packet filter, and perhaps a VPN session to their home or corporate network. Anything else exceeds the capability of such boards quickly.
As I mentioned above, the features you want to use are just as important. IPS and the web proxy are almost certainly a show-stopper if you want to achieve significant bandwidth.
For SOHO scenarios, I usually recommend this appliance (full disclosure: I am not related to the company selling it ). While it is more expensive, it is worth the cost from my point of view.
Thanks, and best regards,