Soapy, my sense of where you're coming from is the way that you, and I'm sure others, perceive the written and video presentations of Ajahn Geoff, and compare that style to the way that Ajahn Brahm writes and teaches on his BSWA site. I have always felt it fortunate, auspicious, that we have both of these monks teaching in our time, along of course with so many other excellent monks and nuns.
Ajahn Geoff has always come across to me as akin to one of my graduate school professors. Sometimes a bit intimidating, but behind the scene much warmer and friendly with colleagues, yet a source of knowledge that is of great value. Ajahn Brahm is more akin to the medical doctor that truly knows his stuff, trained well, is well disciplined, but also learned that part of the delivery of the medicine is a great "bedside manner."
For me, if I have a general sense of wellbeing and am looking for some strengthening of my Dhamma academics, Ajahn Geoff is usually my go-to-monk for Sutta study and Dhammic information. On the other hand, if I am having a rough day, or experiencing some inner turmoil that I just can't seem to shake off, I am more apt to turn to one of Ajahn Brahm's talks on "letting go," or a similar subject. Certainly, he has stated that people in distress or suffering the loss or potential loss of a loved one, have come to him to say that his books or talks saved them from extended grief, or worse. My guess is that at some point in his monastic life, he understood that the way into people's heart and minds was through teaching Dhamma in light of everyday experience, everyday ups and downs, and with some humor interlaced. He's a storyteller with great wisdom, like the Irish seanachi, while Ajahn Geoff, to me, is the dean of the graduate school.
I've noted before that I have spent time at Wat Metta, and been around Ajahn Geoff when he gently teases one of his young monks to a chorus of laughter from the lay gallery. He's not humorless, at all. It's just that Ajahn Brahm may be your go-to-monk when life is hitting a rough spot, and you need both the wise doctor and the bedside cheer to keep you positive and seeing the bright side of life. This is not two Buddhisms, but one Dhamma that is fortunately being disseminated by two very different, but equally compelling teachers.