1. Depends on your experience. Easy to control, but a large amount of features/options to control.
2. Depends on your application.
3. IMHO, yes, as it does not require chipping and has a faster response rate. I chose the EMS over the Hondata because the price of Hondata + OBDI ECU + conversion harness + EPROM burner is much more than the EMS.
4. A standalone fuel management system is a good idea for any boosted application. Type of FMS depends on your specific needs.
5. Yes, EMS supports staged injection (up to 10 injectors). You could not do this with Hondata.
6. Not unless you want something you can modify on the fly without a laptop.
7. Yes. Most people use a GM boost control solenoid and have at it.
8. Both.
9. No. Most people with the EMS just get a replacement distributor cap along with an external coil.