I can attest that Bose is really flat and uninteresting to my ears, but when it comes to say, the 901 Series, which used to be their masterpieces (maybe still are) they utilize reflections like you wouldn't believe! Plus, instead of really designing the speakers to be perfect, they use other technologies to enhance the frequency responses of the drivers/speakers so that they can get away with fundamentally flawed designs (like smaller speakers, for example). This isn't intended to be a slam on Bose. They have a market they shoot for and they do VERY well at filling it. But as discovered in most situations, the Bose systems tend to sound a bit different than other systems and for good reason.
I own a pair of Polk SRS-SDA 2.3TLs and love them for what they do. They're not perfect, but they do widen the soundstage more like headphones will, and the bass frequencies will go very low without a sub (like 25Hz!) if placed in the right room with bracing. However, the mids are sometimes a bit warm. So, I do have to get integrity-checks on other systems.
I think there isn't really one speaker for everyone, and I suggest definitely let your client have you over and let you hear his setup. It could be ill-placement, to some degree, or you'll get some insight to what it is he's missing or hearing wrong.
Best of luck!