Welcome to the sport and the forum!
I think the Custom V and the Skate Banana are about the same flex (medium) and the Banana may even be softer. Unfortunately for you, your 2 goals are at odds with one another. A stiffer board will certainly provide more stability at higher speeds, but a more flexible board will be friendlier if you are transitioning to the park and want to do tricks.
I am not real familiar with the Burton but an upside of the Banana is the magnetraction which will help hold an edge on the icy trails you'll likely by riding. What you really need to decide is what qualities you need based on what kind of riding you want to do. Finding one board to do it all generally leads to making a sacrifice here or there. High speed carving on groomers is kinda the opposite end of the spectrum from a full on park stick.
Here's the Good Ride review for the Banana, if you haven't already seen it: Lib Tech Skate Banana Snowboard Review
Hope that helps a bit.