There isn’t a right and wrong answer to the best. However there are different degrees of QD primer and waterbased systems, and also culture differences seem to figure in choice of water based over oil and microporous over non-microporous.
In 2011 I did the “Mythic house” all acrylic over old oil. It was in semi gloss sheen, which is the same sheen as most high gloss looks after a year of weathering IMO. It was very easy to work with and fast drying was a huge advantage, especially in rain-soaked Britain.
When speccing the front doors, I would have said that oil based onol primer and a Sikkens oil topcoat was as good as it got, which for finish is still the likely case, but something changed in 2010 and their oil undercoat/primer dry times went through the roof, and I found the system almost unusable. The savings on drying times of the quicker drying water based Sikkens Onol primer were significant. It stuck to well prepared old oil gloss and there seemed to be no noticeable sheen difference in the oil based topcoats.
It is interesting how Zinsser has become the go-to Quick Drying primer shop, nothing wrong with that, as the products are strong, but if something goes wrong, you have no comeback from any other brand company if the top coats don’t perform.
If you use a full Zinsser spec,that negates that potential issue, so you are likely on to something looking at the Allcoat system! But be aware that waterbased All Coat is a copy of a Classidur product and I had this from a dec last March who didn’t like the copy.
The worst covering paint we have ever used( white by the way). Nice & smooth to use quick drying, but thats it! Some areas took 5 coats to cover, & this is white over white.
Zinsser QD coverstain isn’t too shabby as a primer/undercoat. I do hear of issues on to glass. I believe oil based gloss still offers a very high adhesion properties on glass, so keep Coverstain off glass and finish with the tops onto the glass.
@pd67 should have some good info to confirm how the waterborne Valtti specs perform on Shetland. And it is a good idea to ask Holmans who rate Repair Care and Valtti exterior paints, saying it is a whole different ball game compared to the repair system with conventional dec trade paint.
Culturally, in Holland, it is oil all the way outside, they use Sigma and Sikkens a lot.
As far as oil based and microporous, Northern Europe seems really into it. However (and @BenSturges may need to confirm I have my Scandinavian trivia the right way round), I believe in Sweden they wouldn’t dream of using a microporous oil based system, preferring to lock the surface down for 10-15 years with the standard Swedish oil paint system.
That’s me all exteriored out