I vote for the Def Tech BP10B, but it's not because my name is AcuDefTechGuy. Oh, no, no.
To me, when played on the same system and source, most good quality speakers will sound very similar with regards to the high frequency and midrange/upper low frequency. Where they will usually differ is in the bottom low frequency 20-30Hz. So in this regard, the BP10B will theoretically outperform the PSB T65.
BP10B: 25Hz-20kHz ±3dB (20Hz-20kHz ±6dB)
PSB T65: 30Hz-20kHz ±3dB (25Hz-20kHz ±10dB)
In real life (practicality), I doubt that I can really hear a difference.

But sometimes it's not about what I need, but what I want.
I want a true full-range speaker that can play 20Hz-20kHz @ good volume.
Sure, I may be anal-retentive. I may be obsessive-compulsive. I may be a numbers freak. I may even be full of it. But "20Hz-20kHz ±6dB" sounds a lot better to me than "25Hz-20kHz ±10dB".
This is what I think. Obviously, you have actually done a comparison between the BP10B & the PSB T-65. And you can't really tell the difference. Right?
It's a toss up. There is no wrong answer here. So you might as well pick the one with the better specs.
By the way, I might have told you this once or twice before, but Julian Hirsch of Stereo Review really loved the BP10B.