It's just a total coinflip. I did it a few times last year and have stopped doing it ever since (as hard as it to resist the urge)
The problem with betting totals in the NBA is the impact of things like pace, free throws and turnovers in addition to just the traditional concerns of offensive efficiency. 2 teams could play a very mediocre game offensively and still score 220 total points...while you could have a game between boston and chicago that is beautifully executed offense which only ends up with 185 points
The only sport where betting totals is a smart thing long term IMO is football. That's the sport with the least amount of variables (all you really have to do is account for offensive efficiency)