ETA: "No Shoots" explanation.I am not an expert on either, so I will do my best to answer your questions. I have shot several USPSA, but only one of the IDPA (last night).
My OpinionFirst and foremost...both IDPA and USPSA are games. If you want training on how to handle yourself in the act of Self Defense (SD), there are a lot of instructors/schools who are active on this forum. PM me and I can elaborate on my personal opinions. Since most of us don't have the time and resources to take several SD classes each week, these matches are the next best thing. With that said, ANY shooting that you do under stress, whether it be a SD class or at a match, is GOOD training. Regarding IDPA being geared more for tactical training, I would say that is generally true. You can wear your CC equipment just the way you normally would and the match could quickly identify what is a good/bad way for you to carry. USPSA is less concerned with defensive shooting and it is more of a strategy game. However, with both IDPA and USPSA, you must make a plan to work through the course as quickly as possible, and then when the timer goes off, try to stick to that plan.
Some Basic Rule DifferencesHolsters: USPSA allows holsters worn on the strong side hip including race holsters, but not In the Waistband (IWB) holsters. IDPA allows only basic belt or IWB holsters (strong side only) as long as they can be concealed by a cover garment.
Spare Magazines: USPSA allows you to have as many magazines as you want on your belt or in your pockets if you must; however, certain placement restrictions may apply depending on what division you are shooting. Number of rounds loaded in the magazine are also predicated on what division you are shooting in.
IDPA allows one magazine in the gun, and two on the hip. You can have extra magazines, but they must be kept in a pocket. The rounds in the first magazine can total 11 so when you load and make ready you have ten in the magazine and one round in the gun. The two spare mags on your belt can have ten each, and the other magazine(s) in your pocket can be loaded to capacity.
Dropping magazines:In USPSA you are allowed to drop a magazine ANY time you want. The magazine may be empty, or it may still have rounds in it.
With IDPA, you can not drop a magazine on the ground with any rounds in it or you will incur a procedural penalty.
Moving:USPSA allows you to move and reload whenever you see fit.
In IDPA you can not move and reload. Also, you must reload while under cover. Lastly, you can not move with an empty gun. So shooting at one barricade until the gun is empty, moving to the next barricade and reloading will incur a procedural penalty.
Course of fire:USPSA...In general, you can engage all the targets in any order or from any position you want, as long as you are within the designated shooting area. A few restrictions apply, but normally the course is set up so that you have no choice but to engage targets from certain positions through the use of walls and other barricades.
IDPA...You must use cover for shooting. "Slicing the pie" is often required. That is to say, you must shoot around walls so that you are partially taking cover, or when shooting through a window (as they did last night), you must shoot through the left or right half of the window. To put it another way, you can not just stand in the middle of the window as you could with USPSA. Also, you must engage the threats in a more realistic manner. As you "Slice the pie", you will shoot targets in the order in which you would normally see them as you work your way around the corner. If you are shooting in the open without cover, you must engage the closest target (most imminent threat) first, and shoot your way to the furthest (least imminent threat) target.
No Shoots:USPSA...You only incur a penalty when you place a round through a
visible portion of a No Shoot target. For example, if a No Shoot is placed behind a target, any rounds that pass through the intended target and also penetrates a No Shoot does NOT incur a penalty.
IDPA..."Pass Throughs" DO incur a penalty. In the same example above, a round that goes through the intended target and penetrates a No Shoot WILL incur a penalty.
Match cost is $10 for non-members of the range and $5 for those that are members of Big Shots. There is not requirement to be a member of IDPA or USPSA.
I'm sure your M&P will be just fine for IDPA and I know you would be good to go for USPSA.
You might also want to check out the "Rock Your Glock" matches at Thunder Alley (
http://www.thunderalley.us/rock-n-thunder/) indoor range in Lincoln.
NOTE: A Glock is
NOT required. You can shoot any centerfire handgun. They are also $10, but they are a little more straight forward for a beginner. You are simply shooting ten strings of five rounds each. Each string is at a different distance and has a different time limit. There is one string each of weak hand only (WHO) and strong hand only (SHO). There is a match this coming Saturday January 26th.
Hope that helps. That is a pretty wham bam rundown of the differences, but I am sure there is much more that I am unaware of. If anyone finds an error in my information, please speak up. But then, I don't have to tell you folks that.
Fly