I'll warn you.  As you probably guessed, I'm heavily biased toward the subaru engine because of my positive experiences with them.  I feel that a standard or multivan (w/ poptop) vanagon can do very well with a standard EJ22 conversion.  Syncros and Westfalias, depending on their typical travel plans and driving styles, might do well to consider the EJ25.
I really like the fact that with the 90-94 Subaru EJ22 and Kep's parts, I can have a vehicle which is officially (even in California) smog legal and will not only pass the check at the DEQ, but if the referee questions the subaru engine in the vanagon, I can show him official ARB exemption documentation that proves legally that my vehicle is legal in all fifty states.  That adds a lot to resale value and my peace of mind.
Although the EJ25, EJ20T (WRX), EJ33 (SVX), and later model EJ22's will likely pass all emissions tests, the owner will experience potential difficulties if the referee questions the legality of the engine.
 
When I get my engine installed (about a month or so at the slow pace I'm going) you are more than welcome to take her out for a drive.  I have an automatic (my last red multivan was an auto too) so the power is smooth and well distributed over the three gears.  The 3rd gear could stand to be a bit shorter in order to handle the high revs of the subaru engine but no drama there.  I hear many of the guys with four speeds get a bigger fourth to give them an overdrive of sorts.
 
Would I install another subaru?  Yes, in fact, since that last time I've seen you I have sold my burgundy van and replaced it with a 91 Multivan.  I'm about half way through the conversion of that van even though the 2.1 still runs strong.  I enjoy the conversion project and feel that the result, a stronger, more durable engine that costs less to repair, maintain, and fuel, is well worth the work to get it in place.
 
As to issues, I can honestly say that all of the issues that took place with my first conversion were a result of my being cheap over purchasing a proper part or doing a job properly.  This time around I'm going with higher quality conversion parts and although I'm doing the work myself, I am purchasing many parts which will make the job easier to do well.  I'm getting parts from all four major vendors....
 
SmallCar's motor mount and VSS
 
H&R's coolant return pipe, modified oil pan (with dipstick thru the license hole)
 
KEP's header, muffler/cat, adapter, wiring blueprint.
 
Tom Shiels coolant kit.
 
Pay special attention to proper ways to plumb the coolant piping, perform the wiring conversion, and the rest is a cakewalk. You're mechanically adept as I remember, you'll have much less problems than I do.
 
That's my input.  As usual, I"ve said too much but hope that it will be of help to you.  Feel free to ask all of the questions you want, I'm glad to talk about it.  And stop by anytime you're in the NW Portland (185th and 26) area.  We'll have a cup and talk shop.