The master electrical certification is optional. To become a master, either speciality or journeyman, you must be a certified electrician and adminstror, in the same speciality.
The master electrical exam is a harder adminstrator exam.
The advantage of being a master electrican is that you only have to renew one certification.
What I would recommend for you is to take the adminstrator exam, if you took and passed the 07, then you could take the 07 master after two years as a speciality electrican.
Note that the 07 (Non Residential Maintenance) exam is the second hardest next to 01, and its a safe bet that the 07 admin and master are the same.