Based on the tone of your question, you appear to believe the two horns are pretty much the same--you are correct. The ex has the new neck series, some mechanical changes, and a few playability improvements. I am a bit confused with Yamaha on this one. Yamaha stated on its homepage that the EX series would be available with and without a high g key starting back in June 2006. As of yet, I have not seen the one with the high g key. Best wishes,

I just tried every soprano on the planet - or so it seemed. Ended up choosing between the 875 and the 675 (both in silver). 675 won because of the fatter, more modern sound. Tried both the 875 ex and custom and, frankly, noticed no significant difference. Both had that more vintage sound, which I did not prefer. Playability was the same. Good luck.