This question was discussed in this BGG thread.
The only answer I found at all convincing was: in a 3-player game, if your hand is marginal, the big bet may convince your opponents to put their own interests aside and work together to set you. If you make a small bet on a similar hand, your opponents might play less aggressively to defeat you--each trying ...
My perspective is having never played Haggis until i played it on the ipad. I have quite a bit of Tichu experience.
The AI offered competition to me for about 5 games. After that i can beat it 4/5 of the time.
So overall i think it is a good way to learn the game, but will not help you get ahead online