Lumping BU and segwit together in that same sentence is a terrible mistake. Segwit has 100x more coders that worked and tested it, and it has been LIVE on testnet for a very long time now, having received 1000s of times more testing than BU has. There is no "rush" with segwit. It was developed slowly and meticulously, and has been audited and tested by many very capable coders. The same can NOT be said about BU.
until last month when gmax found out his going soft approach Luke JR promoted wasnt as soft as he thought because gmax found out only last month that it ran into compatibiliy issues with ASICS that PRE-DATE segwit code.
also last year it took months to convince devs and get passed their ego's about the anyonecanspend. but instead of writing a version that would have been a full network upgrade and an oppertunity to add real features in. they continued as is and done a work around by telling people not to use segwit wallets until long after activation (killing part of their backward compatibility promise) and also by reinforcing their control of a tier network by making older nodes to be downstream of the network.
making segwit such a cludgy bit of code with no promises. just 'expectations' and many if's and maybe's