Obviously im not a coach and have a surface level understanding of this stuff but IMO systems domt really matter that much. No matter how many new ways you want to cloak it or call it something new there are only the same basic 9 routes for recievers to run. Think of the wildcat surprised the hell out of BB the first time he saw it but then pulled out his single wing t defense from the 1940's the second meeting and stonewalled it.
I will jump on
@patfanken way of discribing it like a language because thats the closest way to explian the difference. Most systems including the west coast are very detailed and specific in the way they call the play. X hook y ladder z go protection omega 37 on 3. It removes the thinking or having to process. A Wr can say i am the y and i run a ladder and the rest who cares. Its easy, simple, and specific. Pros are you can get people up to speed quickly and they know exactly what to run everytime. Cons are jeez thats a mouthful and there is zero flexability if the defense calls the right play to shut it down.
The rest is more window dressing about where and how you attack, are you more high risk high reward attacking vertically deep? Air Cordell. Or lots of horizontal screens and quick fast devolping routes streching the field sideways and making the defense cover more ground? West coast.
The EP is a different language entirely. Same play gets called hooks right. From that the entire offense should get a picture in thier mind from the playbook with the rules for that play. Lets say hooks is a 3 wr set that has the x and y running different depth hooks one at 5 yards and another at 10 both on the right side of the formation. The offensive line knows everyone will be sliding protection to the right with the running back running a playaction fake left and picking up any late blitzers that way.
Heres where it gets complicated, thats how its called and drawn up if they are facing man defense that doesnt have a saftey over the top. If they do run into a dime zone coverage they werent expecting the y needs to change his hook to a go to draw a saftey deep. Again i dont know the exact change in call i am just talking concepts. Thing is everyone on the offense needs to read the defense and know the entire play with all the rules.
Pros are short play calls so changing things at the line is quick and easy, hooks arent going to work fine we'll go with crosser and i told them in the huddle thats play alpha so seconds before the snap Alpha go! Its also extremly difficult to stop when the qb and wr are on the same page because the route changes based on the coverage instead of i am running this route and only this route. Cons you need the kind of receiver who thinks like a qb. They need to read coverages in real time AND read it the same way the qb does. Its why Branch was a way better wr here then Ochocinco but didnt work out as well in Seattle.
There was a video of Brady and Branch literally just lining up and looking at each other. No playcall, no words exchanged but just from body lnaguage and the way Brady was looking Branch knew the play and what route to run. In the EP if Brady is expecting you to be at an 8 yard crosser in 1.8 seconds it doesnt matter that you have 3 yards of seperation running a 12 yard dig in 2.1 seconds, he has already looked past you. Thats why Ocho was so frustrating because i saw him still breaking plenty of DBs ankles. The guy could still play and at a high level, just not with Brady.
Going forward i dont care what system they run, its all just the way you call it and how you want to attack. I care that they get everyone doing the same thing and that comes down to coaches effectively getting thier message accross in a way players can use instinctual. Hope that helped with your questions.