I think you need to look at this differently. First separate the DM class from the IDC. You may end up doing them back to back, maybe even in the same place, but they are very different.
Disclosure.... I did my IDC and staffed an IDC at EASE, others elsewhere. Im now an MI, have worked fulltime for about 7 years, and trained hundreds of DMs.
Your DM class is the most important one youll ever take. There are two ways of teaching it, the internship or practical training exercises, which are simulations. The internship takes 6 to 8 weeks. You will work with real customers, in a real shop, with instructors and captains and staff who do it every day. You will fill tanks, carry tanks, learn to tie up boats, load boats, change orings, deal with problem customers, broken equipment, safety issues, scheduling, and a million other things. And study your ass off. You will dive almost every day, 6 days a week. working with pros. You will learn all the REAL skills that are expected of dive instructors, that are not in any book.
OR
you can cram all this into 1 week, no real customers, no real diving, no real classes to help with, just a few simulated situations, using other dive pros as actors. This is the method used by 'instructor factories'.
By the way, this is where the info that you get tested on at the IDC comes from. You will NOT learn or even really review it there.
Now who do think is better prepared to get a job? You are pretty useless if you cant even fill a tank.
All that being said, you are better off going to the carribean for your DM, and take 3 months. You can get your IDC there too, no prob. Make sure that you go with a busy shop, so you can help with a lot of classes and dives. Also choose your instructor carefully, and insist on him/her as your mentor. A good shop will have you work with multiple instructors, but 1 will be your mentor. Look at Honduras, Mexico, Belice, cozumel, it might be cheaper than going to florida, a lot more fun, and youll meet a lot more people while getting real experience and contacts.
The IDC just prepares you for the IE, you will not (hopefully) learn ANYTHING new about diving. BUT YOU WILL BE TESTED ON EVERYTHING! You will have learned this all prior to taking the IDC. All you will learn is the teaching side, presentations, grading, paperwork, etc... This being the case, the best place for your IDC is whatever is most convenient, easiest or cheapest, this not as an important a choice as the DM classes. Here, instructor factories are great (EASE was great, also all the others Ive staffed), they have it down to a system. Prep classes are not necessary if you know the material from your DM class.
Job placement is pretty much a joke, and now Im in the industry, I see it just doesnt really work that way. There may be exceptions, but I wouldnt weigh this too heavily when making a choice.
If you need more info, just message me.