Bought the Speedy and Docomo to try.
With a voltage/current tester, I get the following results.
Speedy Cable Charging G3
Asus Nexus 7 2A charger - 0.7a
Anker 40W 5 port charger - 0.7a
Docomo Cable Charging G3
Asus Nexus 7 2A charger - 1-1.1a Edit. Max is 1.45A.
Anker 40W 5 port charger - 0.9a Edit. The Anker can't do better than 0.9a on the G3. On the Nexus 7 however, the max is 1.65A. Tapers as the batt hits 90%.
Speedy Cable Charging Xiaomi 10400 PB
Asus Nexus 7 2A charger - 0.5a
Anker 40W 5 port charger - 0.5a
Docomo Cable Charging Xiaomi 10400 PB
Asus Nexus 7 2A charger - 1.5a
Anker 40W 5 port charger - 1.5a
Note that the tests are not controlled. Readings taken ad hoc. The Docomo cable clearly charges faster. Interestingly, the Nexus 7 charger is quite capable.
Edit my posts for updates.