Best is directly tied to the amount of money you want to spend.
PfSense running on a Server motherboard is going to get you an insane router but
it'll cost you money for even an entry level device. (Or you can use old PC hardware that will probably not perform well, use lots of power and have stability issues)
Mikrotik personally I don't like because it is more complex than it needs to be. PfSense was able to overcome the complexity, so I don't really see that they have an excuse. That said, it is a lot cheaper to setup for comparable performance.
Everything else comes last but you can get a whole lot of great features and a good product for a lot less money.
You should really look at
www.smallnetbuilder.com, get a router that matches your wallet and what you need.
When we talk about routers, I assume you mean a router and not a Wifi router.
Wifi routers are Wifi access points with router features bolted on top.
Wifi on both Mikrotik and PfSense are bad. In fact they are terrible at that, they use old hardware that is terrible outdated and slow. The newer hardware on both have driver and interoperability issues.
There you are best suited to smallnetbuilder.com, use the router ranker and get a high performance Wifi router.
Typically you use Mikrotik and PfSense to do your router stuff and then plug a wifi access point or router (set to access point mode) into them.
The reason you do this is because both those operating systems offer features you don't get with a soho router.
eg. PfSense can setup
SNORT, proxy (cache HTTP stuff), OpenVPN, local time server, VLANs, arbitrary scripts, massive packets per second performance, etc. Basically stuff you like to have for complex high throughput networks.