Played all of them.
They are similar only in the way of being pretty damn hardcore.
The controls for armored core games are notoriously hard for newcomers and will have plenty of people just straight up stop playing. That said, if you get used to them, they are perfect.
Story telling is also somewhat similar in the way of main character not having a voice of his own and just not a lot of stuff being there on the surface.
As for gameplay, combat is fast, but depending on which one you pick up... it can be extremely fast. Armored Core For Anwser just turned it up to 11.
The games have more customization then any other mech game on the market though(that I know of anyway). With there being hundreds of parts ranging from targeting chips, generators, thrusters, seperate body parts (legs, core, head, arms, stabilizers) to multiple weapon systems (right/left arm, shoulder, back mounts, holsters, weaponised arms) and all of these can often be individually tweaked as well for specific outputs etc.
Depending on how interested you are, you may want to pick up Armored Core V. Sadly the community isn't very active anymore, but Armored Core Verdict Day is releasing by the end of this year and save games will carry over.