SegWit is not hard fork, it is safer to activate, no risk of 2 coins. We have over 80% nodes already supporting it - unlike BU 11%.
Plus the amount of hidden catches in BU is more scarier than what SegWit is trying to sell us: we can start with 'emergent consensus'.
Once we activate BU we will be forever slaves to it. Future upgrades won't be easier or safer with BU.
BU is dodgy at best, but lets be real here.
Nodes-> Barrier to entry is near zero. Sybil attacks are a thing. These combined means it is an unreliable metric to use.
SW safer to activate -> SW nodes will not request blocks from non-SW nodes. Thus if you're a miner you're forced to upgrade even if you're not in the 95%. It also opens an attack vector since SW transactions use anyone can spend. 51% attacks can now
steal people's coins.
activate BU we will be forever slaves to it -> See above: anyone can spend. There is no going back from SW either.