My understanding is that SP hubs, while lighter than Shimano hubs, have more drag and provide less power than Shimano hubs.
Source SON hubs are the best-performing by all accounts. I've had a Shimano DH-3N80 on my main bike for five years and it's served me well. I've repacked the bearings a couple times, and when a bungee cord got stuck in the spokes and wrecked the electrical connector, I was able to replace the part with something scrounged from a cheap Nexus dynamo hub.