If you need explaining what Son brings to the game over Brennen, frankly you're a lost cause.
For starters you should stop looking at G/A stats as if they're the be all. Take most of those Johnson goals - they're tap ins from two yards. Valuable, yes, but indicative of genuine ability, world class attributes, skills you can develop? No.
Go take a look at Son's first goal for Spurs. Age roughly 23, against Palace, takes the ball on the left, beats a man with a brilliant shimmy then smashes it low past the keeper. From that moment it was abundantly clear we had a real player on our hands.
How many times has Brennan done anything like that that? What did he do last year that made you think, wow this guy has some real ability?
How many of his assists last season were brilliant slide rule passes like Son made time and again, as opposed to low crosses into the box any two bit winger from the Championship can deliver?
Sometimes the game needs to be seen with your eyes and brain. Not behind spreadsheets and stats.
A pearler of a long range goal is worth as much as a two yard tap in, same point goes for the difference in type of assist. You have to factor in how we set up and what Ange wants from his wide players too, Out wide leading to low crosses is a big part of that as is my understanding.
If we had a proper CF in the box for most of the season Johnson would have likely picked up a few more assists too