I sometimes suspect 3-2 is best against look inside, because it kind of forces your two best defenders to cover the inside. But 2-3 appears to be good against inside isolation. No way I should have beaten Arizona with one of my best players out, and guessing wrong on game day prep.
Most of the vets claim 3-2 is the strongest defense, even against LI. Supposedly, the way the game engine works, 3-2 will just shut down the guards before they can even get the ball inside. A lot of people claim that 2-3 doesn't really work against anything.