The base Fighter is an extremely weak and boring class, meaning it depends on its subclass to provide all the flavor, power, and identity of the character. This puts a lot of pressure on these subclasses to deliver, and makes it really bad when one fails to do so.

Fighter isn’t a particularly complex class. It's about attacking. Some of the subclasses offer some interesting abilities to assist your team out of fights, but primarily you’ll be getting ways to attack more frequently and a bit better. If that’s what you want out of D&D, you will get it here. 

Battle Master comes out the gate swinging. I desperately am hoping the next edition maneuvers are just baked into the base fighter class with subclasses getting fancy special bonus optional maneuvers unique to each and scaling that doesn’t cost you new, exciting features.

You can do powerful things with Samurai. Advantage on all attacks on command is nuts, and getting to convert one attacker's advantage into another entire attack will make you feel like an unending flurry of blows.

Rune Knight offers fighters a massive pool of resources it has always been in desperate need of. You get a swath of new reactions, bonus damage options, conditional effects, protection features, and weapon improvements.

Psi Warrior promises a fantasy and delivers on it at basically every level. The option isn’t radically powering up every one of your attacks like some other fighter subclasses do, but instead gives you some fun telekinetic tricks to expand out how you can interface with the world in ways you’d want.

Eldritch Knight is at its finest from 3rd-5th level, with decent enough scaling with its spell roster alongside base fighter you’ll never be terribly disappointed with it. Its core features are pretty terrible outside the spellcasting, though, meaning you’re going to have to lean very heavily on your 1st, 2nd, and 3rd level wizard spells alongside extra attack to get power out of this option.

Echo Knight is an incredibly rich option to pick up, but with the middling power from the 10th through 18th level features, you really want to consider multiclassing with this. Getting to 5th level for extra attack then dipping into some magical classes like Trickery Domain Cleric can transform your character into the master of duplications. 

Champion is predominantly a subclass for people who want to build a character whose entire identity is critting. The bulk of the power of this subclass is baked into how critical hits function with advantage, and the rest of the build around it probably seeks to get that advantage however it can with feats, races, and magic items.

The Cavalier has a wide breadth of possibilities in a game full of creatures of all types. If that’s something you're interested in, Find Steed in the Paladin class is the perfect place to start. If Paladin isn’t for you, I guess technically you could opt to try Cavalier.

Banneret isn’t particularly complex, nor does it give you a robust new pool of resources to play with. It lacks even basic new abilities when you’d expect to get them, instead slightly improving the effectiveness of prior abilities.

The Arcane Archer in its current form fails to deliver on this fantasy in a spectacular fashion that leaves the user frustrated and disappointed.