The Sony WH-1000XM3 and Bose Noise Canceling Headphones 700 both promote faster charging over USB-C technology but let's see how they compare using the GRL-C2 USB PD Tester and GRL-PSP Power Analyzer software from Granite River Labs. Note the Sony WH-1000XM4 should have the same charging behavior as the Sony WH-1000XM3.
For full charging, the Sony WH-1000XM3 needs 3 hours while the Bose Noise Canceling Headphones 700 needs 2.5 hours based on Sony and Bose product claims. We found from the testing below that Sony is more conservative while Bose is more aggressive with these claims.
Charging very much depends on the type of USB Source you connect to.
Let's first look at charging the headphones using a USB power source that doesn't support BC 1.2 (meaning 5V@1.5A is not supported).
Using the GRL-C2 USB PD Tester as a 15W (5V@3A) USB power source but without BC 1.2 support, both headphones pull a maximum of 2.2-2.3W during charging. We can see that it takes 3.1 hours to charge the Bose Noise Canceling Headphones 700 to full from 0% battery vs 2.5 hours claimed by Bose. We can also see that it takes 2.7 hours to fully charge the Sony WH-1000XM3 to full from 0% battery vs the 3 hours claimed by Sony.
We can also see that the Bose Noise Canceling Headphones 700 stays in fast charging mode where 2.2W of power is used continually for about 2 hours. Interestingly, the Sony WH-1000XM3 only stays in fast charging mode (2.3W) for about .9 hours and takes a much longer time than the Bose headphones to gradually reduce the current before the battery is fully charged.
Given that the Bose Noise Canceling Headphones 700 is obviously charging at a higher level for a much longer time period, this implies a much higher battery is also used. From these charging plot curves, we calculate that the Bose Noise Canceling Headphones 700 has 5.4 Watt-hours of battery capacity, which is twice that of the Sony WH-1000XM3's 2.7Wh battery, despite the Bose headphones being slightly bulkier.
With Bose claiming 20 hours of use with the Bose Noise Canceling Headphones 700 with a larger 5.4Wh battery, while Sony claims 30 hours of use with only a 2.7Wh battery in the Sony WH-1000XM3, this implies that the Bose Noise Canceling Headphones 70 has much higher power consumption (.27W per hour) vs the Sony WH-1000XM3 (.09W per hour). A higher power consumption may explain why the Bose Noise Canceling Headphones 70 needs a larger battery and much longer fast charging time period.
Sony implies that 1.5A charging is supported but we only observed .45A being consumed even when using a charger that was 1.5A capable, which implies BC 1.2 support. Fortunately many USB Power Delivery (PD) chargers support BC 1.2 (USB-IF certified USB PD chargers all support BC 1.2).
Using the BC 1.2 capable Apple 18W USB-C Power Adapter to charge both headphones, we can see a big difference compared to when using a non-BC 1.2 charger. The Sony WH-1000XM3 fast charges up to a max of 6.75W and this >2.3W fast charge mode lasts for about 50 minutes. This initial quick charging allows the Sony WH-1000XM3 to finish charging to 100% in about 1.9 hours vs the 2.7 hours seen earlier when using a non-BC 1.2 USB power source.
On the other hand, the Bose Noise Canceling Headphones 700 does not take advantage of BC 1.2 charging despite its larger battery capacity, and a max of 2.2W is still seen when charging with the Apple 18W USB-C Power Adapter.
Even though both the Bose Noise Canceling Headphones 700 and Sony WH-1000XM3 use the USB-C connector, the actual charging technologies used are still from the legacy micro-B days and don't take advantage of the >7.5W easily supported by USB-C technology. One reason for this may be that while the Sony WH-1000XM3 is fast charging with a BC 1.2 charger, the headphones reaches a max temperature of 51 degrees C. By contrast, the Bose Noise Canceling Headphones 700 keeps its temperature below 32 deg C through its slow charging approach.