As per J1 rules, one cannot change sponsor for the J1 as the school issuing DS form is your sponsor for the duration of the stay.
The difference is, once finished training - presume at least CPL, likely with CFI as well as that's the point of doing J1 visa, one could find instructing job with another school (that has vacancies and/or pays better)
There have been some negative experiences voiced as to Ari Ben's willingness to organise graduate's transfer between schools - no wonder if the guys make business out of paying international students less than US citizens. It's not just this school that has lower rates for graduates instructing, but.. Read for yourself on other AB/EFT threads.
Good point regarding 'safety pilot', good for Europe if you're the one under hood, teaming up with local student happy to be safety pilot. No point having 50/50 share of time.
The J1 visa forms could be issued until NYE this year, so no point scaremongeing. If (why?) a school doesn't want to issue them earlier, OK. BUt won't be able AFTER Dec 31 2009. I wish it weren't happening, but..
With the changes in job market in the US (and elsewhere) there's less CFI jobs around in the US. I've been watching JSfirm and some heli (SSH influence in rotary CFI job market as well) websites and there is definitely less fresh CFI jobs advertised. Meaning? More CVs flooding the schools or instructors staying longer. If your objective is to rack up the hours, J1 is definitely worth it (provided one has a CFI job). There are few more J1 schools for fixed wing in the US, but only FAA stuff.