My money would be on ex-BR Mk1 GSVs, looking at it just from the numbers.
22 GSVs vs. 6 Dutch vans, and they can run with current IRM PRs and future IRM PRs, current MM Cravens and future MM Cravens, RPSI Cravens set...
...and more importantly, they share cross-platform modularity with Accurascale BR Mk1 vans / coaches.
Not saying that I don't want Dutch vans, I'd love a few, but I'd also expect, and be prepared, to pay a significantly higher unit price for them.
I can't speak for other members but if an ex-BR Mk1 GSV was going to sell for €60 or €70, I'd happily pay twice that for a Dutch van.
Likewise with the Tin Vans / HLVs, I'd be happy to pay twice the price of a regular coach for one of those, and would buy more than one.
Damn you, OCD.