And we have a winner.
The 310 and Navajo were out. Even though there might have been a way through the icing at altitudes those two could do, wanting to stay at a reasonable pressure altitude for the passenger may not have been feasible while staying away from ice. The duration of the flight here was a consideration as well - the crappy weather was heading right for the pickup point, and 24 hours later it was so bad that the airliners weren't going in and out. So an overnight was not an option.
The Malibu would never have been a consideration for me. Even though it can fly at appropriate altitudes to get above the weather, a piston single over the North Atlantic in January (at night for the return trip) is not a good idea, in my opinion. Doubly so for a piston single with a high rate of engine failures. If it was better weather and we weren't flying over such inhospitable areas, maybe.
The Lear would've been nice, but the trip required a stop anyway on the return trip to clear customs (international). There would have been a time benefit, maybe even a significant one, but the extra cost would not have made it worthwhile. A lower-cost smaller jet might have been a more viable option, but wouldn't have been available.
We ended up taking the Cheyenne II. With the 80 kt winds at FL250, we were doing 300 kts over the ground on 400 pph combined, made it there in just under 4 hours including the climb and an approach. Flying back home we stopped for clearing customs on what by then was the western edge of that bad weather. Flying home we were at FL200 for both legs. 500 pph combined and only 180 kts GS. But we had a nice 4,000 ft cabin pressure, which was comfortable for crew and passengers.
It was 10 hours of flight time. Part 91 operation and I've had much longer days than that, but it was nicer having two people for that long in one day.