If you want the higher rated spare, get the higher rated spare. You may not have a blow out for years and may want to change out all of the original tire at that time. If you do have a blow out and you believe that your other tires are fine, keep each axle matched up with the same tire size, ie. when you put the higher rated spare on and get the blow out fixed, put it on the same axle as the higher rated tire and use the tire on the trailer (smaller one) as the spare. until you cycle through them. But try to keep the same tire size for the long term on the same axle.
2013 Forest River Salem Hemisphere SBT312QBUD
2001 CrewCab F-250 7.3 PowerStroke Diesel
SuperChip, BTS transmission, 6.0 Trans Cooler