Leatherhead
Possibly a Idiot.
So, how do you chose which weapon(s) to use when you make a fighter character?
Making a character is quite different than being in the middle of a campaign and making due. One of the people I play with made a traditional Sword&Board Fighter and then picked up a magic Flail. Thanks to the smoothed over class features and feats, such an organic switch is easy and practical. And quite frankly, DPR isn't the only measure of combat effectiveness, especially when you allow feats, it just happens to be the lowest common denominator. The battlefield control of Sentinel gives monsters far more trouble than either of the -5/+10 feats. Right now we are in a really good spot where you can pick a weapon type or fighting style and make something that has noticeable combat impact (as a Fighter should have). Those other threads are mostly talking about how the 2WF is in a weird spot for basically every class that is supposed to be able to use it due to unintended consequences of action economy.
That being said, some weapons are designed for a Fighter as opposed to other classes.
For starters, any Simple weapon with a Martial equivalent (except the Trident, wtf is up with that weapon). You basically payed to use them by selecting the class, might as well reap the benefits of them.
Sometimes similar grouped weapons have a bend one way or the other. The Greatsword is a Fighter weapon and the Greataxe is a Barbarian weapon. They benefit from most of the same mechanics, save for two class mechanics that are based on the weapon damage die size. The difference between these two weapon types is small enough that I would probably use a magic "non-fighter" weapon if I managed to get one.
An extreme example is the Bow VS Crossbow. Without feats, using a Crossbow would be totally impractical for a Fighter. With feats, the Crossbow becomes better, but that is expected with an expenditure of resources. And giving a (reasonable) magic alternative wouldn't be attractive enough to convince me to switch over in either case.
Now, once you account for the weapons that are designed for a Fighter, we can come to the weapons which are basically outclassed by other similar weapons. That Flail, for example, is just flat out inferior to a Warhammer. Granted, in most situations that Versatile option isn't going to come up. But when making a character, unless you are being narratively limited by God or Country, it is realistic to go with the weapon that gives more options. In these cases, I would pick up a magical "inferior" weapon, unless I was specifically using the weapon for the option. Such as using Versatile weapons for a two-handed small race weapon.
Finally, after everything else is considered, there are some cases where weapons are used explicitly for a "build", like the Quarterstaff. You can make an amazing Quarterstaff Fighter, but it isn't something you would naturally think of unless you have a high degree of rules mastery.