I may be slightly biased on this but i would go for the BOSS setup
When you break down the prices, i think the BOSS or the Ultimate is a better value IMHO
OME kit base price: $825.24
Add in assembly: +$100
Top plate spacers for a full 3 inch: + $60
Diff drop: +$30
OME total: $1025.24
BOSS kit: $1089.99. Already assembled, includes the diff drop and is adjustable from 0-3.5 inches.
You don't have to add all the extra stuff to the OME kit but adding them makes it more of a straight comparison.