The issue is iPad using a WiFi router. Not while connecting via the phone.
Been going on since the original iPad, and iPad2
Just Google speed test. Any of the top listings will work. I've used speedtest.net just fine.
Test on a netbook, laptop, desktop, wired & wireless to get a baseline of your ISP and router first.
Then download one of the free speed test apps for the iPad, and test again. Those of us who had the problem becasue of the noticable difference, were then looking for answers, and found them here.
Slow speed problem identified, answer found, router setting changed, slow speed problem fixed!
Go to the router settings, change as advised, test again, see and experience the difference. At least, that's what most of us got after making the changes to the router. Furgettabout it after that!