Internet Download Speeds Slower on iPhone?

Does anyone have any ideas as to why the download speeds I receive on my iPhone are significantly slower than those registered on my Macbook Pro.

I have an ultra-high speed connection, and as measured by SpeedTest, I get about 200+ Mbps download speed.

On my phone though, I rarely top out at over 20 Mbps.

Is this due to the phone being slower for some reason, the App I'm using to measure, the modem/router itself, etc?

The phone is the newest iPhone 6, and my ISP is TimeWarner. My modem/router is an Arris model (Model #DG1670, I believe).

I use Ookla speedtest for all measurements. I notice that my iPad is also slower, but it will go into the 50s on the SpeedTest Measurement.

The model router is dual band, and I notice similar effects on both 2.4 GHz and 5 GHz. The tests are measured standing right next to the modem at a distance of 2-3 feet with nothing in between the phone and the modem/router.

Just curious if people think it's the phone, the router, the nature of the App (e.g., are phone download tests just not accurate/precise).

Please help. All ideas or opinions are encouraged!

Thanks!