Certain attacks into caves are not able to be defended. Therefore cave attacks provide an alternative to Ls and other multiple loop threats for forcing a win. The second significance of caves is that it is possible to have caves in which there are no legal moves. Lines and loop threats may be defended permanently by linking them to a path going into a dead cave. Detailed long term strategies are very hard to form.
Most threats tend to be fairly localised so the game tends to progress from one hot spot to another.
TRAX is more of a waiting game - playing for long term advantage in terms of potential, while seizing whatever opportunities your opponent gives you. Keep your options open. If a path can be used for either a loop or a line, don't commit it either way. Work on something else and wait for your opponent to make the move for you. That way you gain a turn.