Hello! I do teach both.
The 9 week GMAT course will be more than enough for the EA (and is, in some cases, overkill—for example, this course covers geometry, which mostly does not appear on the EA).
There are also, of course, differences in terms of time management and test strategy. If you take the GMAT course, you'll just need to take that into account. We have an article series that explains the major time management strategies for the EA and you'd just want to mentally substitute those when these topics are discussed during the GMAT class.
https://www.beatthegmat.com/mba/2018/01 ... ent-part-1As you noted, the EA course is shorter (10 hours of class time plus two 1-on-1 coaching sessions and spread over 2 to 4 weeks vs 27 hours of class time over 9 weeks for the GMAT class). This isn't so much because there is less to learn—the EA still covers most of what is on the GMAT—but because the score requirements for the EA are more lenient. (The GMAT has become something of an arms race.)
Basically, you need a really good GMAT score but only a good-enough EA score—so while there is still a lot to study for the EA, you don't generally have to go as far with that study as you do for the GMAT.
We do have some students who choose to take the GMAT course even given all of the above because they do want more in-class instruction time and/or want to spread out their studies over a longer period of time. That approach is absolutely fine as long as you are just educating yourself on the differences and adjusting accordingly. (You might also specifically want to seek out a GMAT course taught by one of our EA instructors, so that the teacher can better advise you during the course. I don't know where you're located, so I don't know whether any of our teachers in your market also teach the EA. You can email our student services team to ask:
gmat@manhattanprep.com.)
One more thing: The GMAT program has coaching sessions as an add-on (for a fee). I'm not advising that you spend more money
but if that is not a concern for you, then you might do a GMAT class with an instructor who also teaches EA and also purchase the coaching sessions. You can then use those add-on 1-on-1 sessions to delve more into EA-related topics (time management, IR, etc).