Obstruction vs. Interferance

Question
Can you clarify the differences for obstruction versus interference? The situation was as follows:

A play was made on a runner sliding into 3rd base. The ball went by the 3rd baseman. When both the runner and fielder stood up, each going the opposite direction (the runner towards home plate and the fielder to chase the ball towards the bullpen)a collision happened and both players went down.   The umpire called obstruction and awarded the runner home.  

The questions are: What is the deciding factor on a ruling like this? Does one call take precedence over the other? Also, is a dead ball immediately called after obstruction? IN this specific case, the play was stopped by the umpire and the runner jogged home.

Thanks

Answer
The decision for the umpire in this situation was made based on where the ball was. Since the ball was not immediately in the area of the third baseman he does not have a right to a clear path to the ball. A dead ball is necessary and the umpire will give the runner, based on his judgement, the base in which he believed the runner would have reached had he not been interfered.