Is turning obstacle avoidance off the same as sports mode?

[The Flying Swan]

I usually fly with obstacle avoidance on, but recently I've been turning it off for long distance flights to increase speed. I've noticed that it's behaviour with OA switched off is very aggressive. It almost flies perpendicular to the ground and the air breaks are slow to respond. It's almost identical to sports mode. Speeds are nearly identical too. I'm sure it didn't used to be this aggressive.

Is this normal, and if so, what exactly is the difference between sports mode and OA Off?

 

[Meta4]

With OA off, your Phantom is in P-GPS mode and will achieve about 15 metres/sec in still air.
It's behaviour is not as aggressive as Sport mode.
In Sport mode the Phantom will tilt further and get to 20 m/sec.