The main things on the HUD that I find helpful to look at are
1. paint remaining
2. little bars of how many people on each team are remaining.
3. Scoreboard
If you don't know how much paint you have it can get ugly.
If you don't know how many people are left you can kill them at the wrong time (done that).
Scoreboard tells you how far above your deaths you are, how others are doing and most importantly, whether that last person left on the other team is a fantastic player or an average one, which can determine the strategy.