Each can be as good or as bad as the people involved. Harvard has a first rate crew, and I've heard good things about Chris and the crew at Riverside.
Some differences -
USPSA/IPSC offers divisions ranging from "production" to "full race" - IDPA is limited to defensively oriented guns (that being said, I would not want to be shot with a race gun
)
USPSA uses "hit factor" scoring (points/tie, weighted by the rounds in a stage). IDPA uses "time plus."
USPSA allows its members to vote for the organization's directors and president, and is incorporated as a 501(c)(3). IDPA is incorporated as a for-profit, and does not permit anyone not holding a seat on the board to vote.
USPSA offers more services to clubs than IDPA (on-site RO courses, full time staff dedicated to USPSA only, etc.) , but USPSA clubs pay a per-shooter fee for each match to USPSA.
IDPA requires persons shooting matches to join after one event. USPSA does not.
USPSA runs a national classification system, with on-line access to classifier scores. IDPA members are self-classified using a simpler process.
USPSA is part of IPSC (the world organization,
www.ipsc.org, which has afifliates in over 60 countries - meaning that matches are available in most of the free world, plus Massachusetts, New Jersey and California.
USPSA is making a push into Three Gun and Multi Gun matches (multi-gun is similar to three gun, however, you use more than one gun in a single stage). I am not aware of any IDPA matches with a rifle or shotgun component.
IDPA uses Microsoft ASP for their web site
http://www.idpa.com. USPSA uses Linux and PHP
http://www.uspsa.org. Both sites are worth a visit.
Rob Boudrie
USPSA Area 7 Director