Well with Tubby's Ball Line defense, its a defense that's built upon the fundamentals of the game, you know things like staying between the ball and the basket at all times. The ball line defense doesn't allow for much gambling in the the passing lanes. If you rememeber this is one of the main problems that Tubby had with Rondo. It's like the old addage with this type of defense, better safe than sorry. In the ball line defense when the offense passes the ball in the corner the defenders form almost what looks like a traingle around that ball. You have the main defender on the ball then have a low post defender that shifts over to play help defense while having another perimeter defender also shifting over. This side of the defense is called the front side, and leaving the backside open because the other remaining two defenders are also playing help defense but on other men. Now if a ball is passed over to the other side then the defense shifts over to its side. If the ball is passed inside then the low post defender is already on him but a perimeter defender always slides down to help on him. So in other words with the ball line defense the players almost never gamble in the passing lanes, they always stay between there man and the basket and there is always a man that helps the main defender.
Gillispie's Man-to-man defense does a lot more gambling in the passing lanes. The principal is the same to stay between the man and the basket but it gives you freedom to gamble in the passing lanes. This is one of the biggest things Gillispie wants the players to do in this defense, he wants them to play the passing lanes, where as the ball lines doesn't play passing lanes. Gillispie's man-to-man defense also contains help defense but isn't used the same ways. Players in this defense may flash out on a player out on another players man in the perimeter and then switches back to his own man. This type of flashing out is prohibited in the ball line defense. It also is built on keeping the ball out of the lane just like the ball line is, but because there players may slide down to help the low post it leaves the perimeter open, thus open three point shots happen.
Gillipsie's defense is more effective with long and athletic players. In Tubby's defense the players don't have to be as athletic because you rely on your teammates a lot more.
I'll start with the ball-line defense...It's mindset is very similar to a zone, although in most cases, Tubby's teams run a man-to-man. He usually switches to a zone on out of bounds plays. But the ball-line defense is meant to deny passes to the interior, but allow passes that go away from the basket. I think Tubby calls these "non-threatening" passes or something along those lines. This helps keep the ball out of the paint, but it does make the perimeter a bit more vulnerable. Although, the entire point of his ball-line defense is to force teams to shoot from the outside rather than in the paint. Sometimes it burns him when teams get hot, but thats the nature of any defense.
As for Billy, what i can see is he is much more of a denial kind of guy. Loves to pressure passing lanes making it difficult to get the ball to the wings, from which point entry passes to the paint become much easier. So, essentially, he is also trying to keep the ball out of the paint as much as possible. Billy rarely switches on screens, so hedges, help defenders, and quick recovery are extremely important aspects of Billy's defense. The main idea around Billy's defense is never leave your man. While Tubby's defense was more prone to open perimeter shots, Billy's is more prone to being broken down by the dribble. But, either one can be stopped by solid execution.