Here is an image of todays Grib File showing Visions Current location (green marker) with the weather forecast time of ~Midnight Sat Night/Sun Morning. The white dot is the 39/39 waypoint that Bill has been considering and you can see why Expedition has been suggesting they stay a bit further South to stay on the favorable side of that low pressure system. It sounds to me like Ken thinks the computer model is over-predicting this low and it likely won't be as significant as as this image suggests which is why he wasn't as worried about venturing further north. Plus, what I don't have plotted above is where the boat will be at this time. Sorry I don't have expedition on my laptop anymore so am having to use a free grib viewer (predict-wind.com). If the boat continues on its originally planned route, I think it would be located at approx 42N/42W at the time this weather is being shown, which puts it just at the edges of the orange/red to the left of the N in North Atlantic. If they stay south (heading towards 39/39) then they would still not quite be at the white waypoint as the low moves east and then north. Either way, it looks like they will see 20ish knots from the NW, but should stay out of the nastier weather to the north.
For reference, here is what the weather is showing they have out there right now:
Much more benign and you can see why they can't go due east easily as that would be nearly dead down-wind. As the wind swings to the NW they can stop heading NE and head more East to stay south of the low.
Hope this helps interpret what they are talking about.