Hey walsheesh,
One thing that is important if you choose the PM is that all of us have taken a leap of faith when we placed our orders! This Van is in its first year of production in North America although it is only a rejigged version of one of the best selling vans in Europe; you still need to take the leap.
There have been a number of hiccups off the get go and as far as I can tell all of them are specific to either the new upgrade or startup learning curve in the assembly line. You can reed about most of them on the forum. I hoping most of them will have been worked out by the time they made my van!
I ordered my PM 3500 159wb Ext for the same use as you; Climbing/windsurfing/Mtn biking.
after weighing all the pros and cons I chose the PM for the volume to length ratio. You get a lot more space with the vertical walls and the added width of the PM. As far as I know the PM is the only van you can sleep sideways in without adding flares.
I have a Toyota Tacoma now and the PM Ext is only 1ft longer than my Tacoma. The PM front wheel drive allows for more cargo space with a shorter overall length.
The significant cost savings of the PM has allowed me to reallocated the savings to camperize the van.
I am still waiting for my van so I can't comment on it critically, but I did test drive both the PM and the Sprinter. The PM does drive much better with less roll in the turns.
Things that I may not be happy with are: clearance for rough roads, Seat comfort, seat adjustment is complicated, no tilt steering just telescoping, only arm rest on one side, inside door handle is flimsy, a small but all so important feature coffee cup holder is out of reach in the PM

. I'm sure I can make grounds for all but the lack of steering wheel tilt.
I am going with the up front galley (Euro style) as well. We will build a high bed in the back with all the gear storage under the bed. We are forgoing a bathroom and using an outdoor shower to gain more storage for gear.
You may want to consider using a tray slider/cargo bed slider for the garage. I have been using one in my Tacoma for many years. They increase storage space and keep gear accessible and organized.
Best of luck on your choice
Dave