Much more Smile has a wider coverage that NTEL and Spectranet, you can access Smile 4G LTE network in Port Harcourt, Lagos, Abuja, Asaba, Ibadan, Benin, Kaduna and Onitsha, while Spectranet is only available in 4 locations in the country as we rightly pointed out here.
Talking about speed and efficient 4G network, Smile is Got it better than Spectranet, however some people have argued that this is largely dependent on locations, but base on personal findings, whichever location you may be Smile 4G LTE offers better speed and overall quality browsing experience than Spectranet.