Single wheel vs duals and electric brakes

[Southside]

I am trying to spec out a new gooseneck trailer that will be rated at 24,000 lbs.  Most off the shelf trailers come with dual tandem axles, 16" wheels at 3,200 lbs per wheel rating when dual.  I have found 17.5" wheels and tires (16 ply) with 6,000 lb + ratings when single.  To me having 4 less tires and wheels is less weight, less rotating, less balancing, lower overall replacement cost.  What advantages do you see by having duals vs singles on the axles given the weight rating will be the same at the end of the day?

Also, does anybody have experience with electric over hydraulic disc brakes on trailers?  Do you get improved braking? How is the longevity?  That adds $1500 to the trailer, trying to see if it is worth it. 

Thanks in advance.