Install lte discovery. You can see what band. This can make a big difference, for example, my Verizon Samsung Galaxy Note 4 doesn't support lte band 2,but my Verizon Samsung Galaxy S7 Edge does. On the note 4, I can get speeds well in excess of 100 mbps on band 4 . On the s7 edge, I can get the same when on band 4. But on band 2,I see speeds around 30 mbps.
That's why I ask which band on both phones. Because even on the same carrier, a different band can yield substantially different results.
You can get a micro to nano sim adapter and pop the s7 sim into the note 4.