Jack, you just don't have enough TD engine swaps on the go yet, do you?

Everything is a compromise when swapping Westy motors, but of these two choices, the ideal motor, cost permitting, is definitely the 1.9 TD. At least, I went 1.9 TD in mine, and have not looked back.
Neither engine will be a rocket in a Westy. You're talking about a vehicle that can approach 5000 lbs when fully loaded.
I have a Giles pump & pretty efficient intercooler in mine, and given the limitations of the vehicle (ie. its heavy weight and appalling aerodynamics), with those two mods, it has acceptable performance. I can easily keep up with city traffic on accelleration (thanks in part to the insanely low transaxle gearing on a Vanagon - even on a 5 speed). Highway power is also acceptable, but depending on transmission and tire size, you're turning close to 4000 rpm at 70 mph, so the top speed is limited by your noise tolerance. Extra sound insulation is a MUST for this kind of swap, IMHO.
The 1.6 TD Vanagon was available from the factory in Europe. Mr. Brickyard here was posting about one that he was working on (the HOT HOT HOT thread). Hopefully he will chime in on his experience.
I wouldn't worry about the 1.9 not liking to rev as much as the 1.6. With the smaller turbo on the 1.9, you're in boost quicker than the 1.6, and off- (or low-) boost torque is fine, in my experience, at least with the fuel turned up & an intercooler. I found the 1.9 TD in the Westy, without intercooler and fueled at original factory settings, to be a truly gutless POS. The engine desperately needs more fuel than factory (car) stock when installed in a Westy, and I'm sure the problem would be even more accute in a 1.6 TD.
Even though Giles has hacked my governor, I'm hesitant to rev the snot out of the engine in such a heavy vehicle anyway, not to mention that anything over about 3900 rpm in a TD Westy will rattle the cabinets, pop-top struts, tables, and the fillings in your teeth.
On a purely mechanical objection to high revs (mixed with my paranoia and inherent mechanical conservatism), I think the guys here who are pushing the TD engine to the limits in their cars, may well find those limits a lot sooner on any Vanagon, and MUCH sooner in a heavily loaded Westy. I think oil temperature is the achilles heel in a TD Westy, probably on both engine types, so plan on a better aftermarket solution for that, even before intercooling.
Ideally, a person would test-drive a Westy with each type of motor in it, first, before going down this dark path themselves. I think you're around Portland, OR. The closest TD westies I know of that are "near" to you are in Vancouver, Canada, and one guy in Victoria, Canada who is installing a 1.6 TD in his westy (he posts here as "Westy TD"). Maybe there's someone closer who would let you test-drive their Westy, first.
Good luck! (And finish that Quantum, first!)