I would go for a ventile, not because I'm blindly following anyone, I've been using the fabric for about the same length of time as the said gentleman. In its modern carnation it was plugged by Survival Aids (when Freddy Markham was still at the helm) which is where I and no doubt Mr Mears first encountered it.
The Double Jackets are slow to dry, granted, but the single layer dry fairly quickly, even compared to some synthetic shells.
They are not completely waterproof (but are very breathable), and if you choose the right garments underneath you create a similar system to the Buffalo gear ( but fire resistant) ie - wind can't get in to chill the moisture in your clothing.
Ventile is robust, leaves Goretex way behind on this one, and if it tears, you just stitch it up, the same goes if you want to alter it.
I can use the ventile year-round, in summer worn as a shirt with nothing underneath, in winter it protects my insulating layers.
Longevity, ventiles become old friends, we live in a "throw-away" society, most modern fabrics have a "shelf-life", we are all conned into having the latest (it what makes big business). So what happens to the "cast-offs"? they are either buried or burnt and thats crap for the planet and future generations.
I have just made a new ventile, my old one has a new owner and I know it will still give years of good service, its twelve years old now, cost £149 then, now Goretex has a working life of three years, so if your shiny new goretex cost you £100, you still will have got thru 4 in the last twelve years (and you don't see many good waterproofs for £100) you do the maths! which fabric is expensive?
Swanni's are good (also marketed by Survival Aids in the UK first), but a tad too warm for year round outer-wear.
I think ventile is a good fabric investment for long-term bushcraft use, it won't suit everyone (a bit like Buffalo gear), its probably not perfect, but I,ve had thirty years doing outdoor stuff to think about it (no snap decisions here!) and its my choice.
Neil1