The J40 is a more deluxe looking instrument. Usually, the higher the number, the higher the trim level. so the J40 would have "40" level trim as opposed to the "28" level trim on the OM. The OM on the other hand, will be a smaller and therefore more comfortable guitar. The J40 will be louder, the OM will be punchier. If you want a fancy smaller guitar, the OM 45 or the 000-42EC would be good choices, but a little more money that the J40. You will need to play both guitars for at least 20 minutes to see which one you are comfortable with. If you are not comfortable with the larger J40, you will not like it; likewise, if you don't think the OM28 has enough abalone, etc., you might not like it either. You want a guitar that looks attractive to you and is also comfortable. Comfort should come before looks. If you are comfortable with the J40, then that would be a good choice. As far as pickups, I wouldn't get a pickup with the Aura system. I had an Aura pedal once and I returned it. My Martin already sounded better than any sound the Aura was capable of, so the Aura just got in the way. I ended up with a Fishman Ellipse Blend pickup system. It has a bridge pickup and a condenser microphone inside the soundhole, and I can blend between the two. I really like this pickup, but I'm not sure if it is still available. If you can find one, you'll love it!!