How to reproduce:
1. Open the attached project
2. Open Test2 scene
3. Build and run Test2 scene on Android device
4. Press the button "Download from the Cache by UWR"
Result is around these values:
Loading Time was - 00 : 00 : 329
The Instantiate Time was - 00 : 00 : 76

5. Press the button "Download from the Cache by WWW"
Result is around these values:
Loading Time was - 00 : 00 : 168
The Instantiate Time was - 00 : 00 : 57

One can notice that loading asset bundles from cache by Unity Web Request is slower than by WWW. The bundles are uncompressed for both cases.
Note: I haven't been able to reproduce it in editor

DUT(reproducible):
LG G5 [LG-H850], Qualcomm Snapdragon 820, Adreno 530, OS 6.0.1

Reproducible: 5.5.3f1, 5.6.0p1
Not reproducible: 2017.1.0b1

Not reproducible: For reliable measurement both WWW and UnityWebRequest should be used at least once before starting measurement