Bo doesn't trust Dyson because by the final episode of S1 she realises that he has been essentially deceiving her for the previous dozen episodes. He has known far, far more about her from the start, but still let her flounder around in the fae world without letting on or helping her discover the one thing she wanted to know about. Whether she trusts his motives or not, she realises she can no longer trust his word.
And, as another poster said, Dyson is completely indoctrinated in the Light fae ideology. He usually won't act unless under orders, even at the expense of lives, and that puts him at odds with Bo in many respects. Dyson is something of a bigot regarding humans in particular, and that's a key sticking point for Bo. For his part, Trick's motives are obscure and he too lies to and deceives Bo when it suits him.
Both Dyson and Trick persistently withhold the truth from Bo, assuming that they know better than she does, or that her investment in individual lives and freedoms is foolish or less significant than their priorities. Dyson and Trick both only offer help conditionally and to the benefit of their own agendas.
Kenzi is a thief, but she's sort of upfront about it, and it's clear she's latched onto Bo with just about everything she's got. She's pretty much always done right by Bo, and she's made her agenda clear from the get go. She's never really lied to Bo or withheld anything, and that's the big difference. In short, Bo trusts her because she trusts Bo.