I have two SP hubs and a Shimano. The Shimano seems to have a bit more drag when I spin the wheel by hand and watch to see how fast it takes to slow down. But riding them I can not feel any difference.

I am not sure if the Shimano has user replaceable bearings or not, if it does that would be one advantage for the Shimano. SP does not have bearings that you or a local bike shop can work on. There are a few you tube videos on Shimano hub bearings, but I have not tried it myself.

I had the two SP hubs before I got a good price on a used Shimano. I found that one of the leads on the Shimano is grounded to the frame, that is not the case for the SP. That caused a lot of consternation while wiring it until I figured out what the problem was.

Taillight, I prefer battery. The wired taillights don't flash and I want the ability to use constant on or to flash. Also, if I am charging stuff, that usually means your lights are turned off. But I want to be able to charge stuff in the daytime while also using a flashing taillight for more visibility. Thus, wired taillight would not make much sense for me. But I use hub powered headlamps.

I am sold on hub units, I would not consider any other.