First of all, I think Howie knew he was going to be the deciding vote. So with that knowledge..I think he voted for Maggie because Ivette voted off Janelle. I think Howie preferred Ivette over Maggie..but wanted to punish her for not taking Janelle with her. Like he said...Ivette made a $500,000 mistake.
Just my take on it ;D
Feel free to discuss.