8T8R antennas have much better performance through Advanced Beamforming. John Saw blogged about this:
To make a real difference, Sprint has to get 2.5 GHz on the rest of its footprint (remaining 30%: Source: Quarterly Investor Update (Page 6)), get 8T8R on as many towers as possible ASAP, get users upgraded to at the very least Triband devices, and even better 2xCA or 3xCA devices ASAP:
Source: Quarterly Investor Update (Page 5)
Honestly, if Softbank dropped the proceeds of the Alibaba sale at Sprint's feet now (Now $10 Billion), that would really help Sprint out on all of the above.