Speed depends on many factors, most are beyond your control. And unless you are side-by-side, accessing the same sites or using the same speed test, it really doesn't mean much.
The factors are: the connection itself, device processor, device memory, your distance to the cell tower, tower congestion, just to name a few. While theoretically possible to get 7.2 mbps on 4G, I seriously doubt one will come close to that just yet anyway, and you won't see 14.4 mbps for a while yet.
