I had the original PBF and loved it, but really wanted to have a bit more options as a coach ... enter PBF, the Expansion!
The first thing you notice when you look at the expansion rules is the addition of 6 new plays--3 each on offense and defense. These can really give you an edge when you read your opponent well, but can also cost you dearly when you're wrong! It makes good decision making a lot more important. It forces the coaches to consider a number of factors.
For example, if you're on defense, and your opponent is facing a short yardage situation, you might reasonably expect a running play (either a standard run or a draw). Do you play conservatively, countering with a standard run defense, or take a chance on a run blitz? If you select the standard defense and your opponent does in fact run, your advantage is far less than if you blitz. On the other hand, if you blitz and your opponent decides to change things up by throwing a short pass, you give away a significant advantage to the offense.
Had this been the only change, I would have been completely satisfied! However, in the immortal words of that old knife commercial ... "But wait, there's more!" Not only do you get the expanded plays, but you get all 32 NFL teams with team-specific charts highlighting each teams strengths and weaknesses (based on actual 2004-05 season stats)!
For example, Minnesota has only average abilities on running and long passes on offense, but excels at the short pass. On defense however, they are average against the run and long pass, but are weak against the short pass. If you are Minnesota then, you might throw more short passes to take advantage of your strengths. If you are playing against the Vikings, you may also throw more short passes to exploit their weaknesses! Couple this with the additional plays on both sides of the line of scrimmage, and you suddenly have a rich and rewarding gaming experience that leaves you hungry for more.
This is a great game. It is statistically sound enough to satisfy the football "purists" while playable enough to appeal to the "let's just play" crowd. I highly recommend it.