Yep, it’s all about the styles and overall sound. Yamaha are unlikely to update the SX700 significantly, so you are basically in the same boat in both arrangers.

If it’s your first pro arranger, and intend to stay with the genre for a significant time, maybe Yamaha may be the better choice as you have an upward or forward path over the next few years, although a used BK-9 could be a nice way to step up from the EA7 without learning a brand new OS. But they’re getting hard to find, and don’t have multipads or a sampler if you use them a lot...

About the one thing I’d definitely give the edge to Roland’s EA7 for is if you are from the Far East or Middle East or other non-Western areas. The EA7 is chock a block full of ethnic sounds and styles from all over the world and set up well for non-Western tunings.