Comparing Ventile and Gore-Tex is like comparing apples and oranges. Two completely different fabrics with two completely different uses.
Ventile is (I believe) better suited to cold, dry environments. For this reason it's used by the BAST. That said, it holds up in rain extremely well considering that it's made of 100% cotton. However, after a couple of hours it starts to soak through, even with a double layer garment. That's when wearing a good thermal such as wool or fibre pile or fleece helps a lot. The first thing that you'll notice with wet Ventile is that it gets stiff like cardboard and then it starts to become heavy, almost like wearing a suit of armour.
But this is only the fabric doing what it was designed to do, it gets wet, the fibres swell, you're supposed to stay dry. (Sortof) Having to put a soppping wet Ventile anorak into your tent every night for two weeks in Och Laddie Scotland doesn't sound very enjoyable to me. I like to brag about being BCUK's resident outdoor clothing fabric junkie and in my narscissistic opinion, you're much better off using Ventile when it's cold and snowy.
Now on to Gore-Tex....
Gore-Tex is made from a waterproof breathable laminate of PTFE (think teflon plumbers tape) with billions of little microscopic pores in it. These pores are too small to let raindrops in, but large enough for perspiration to escape. Standard WPB garments are generally waterproof to a hydrostatic column of water measuing around 20,000mm but some are much more. Gore-Tex, Event, Hyvent, Entrant, and all the rest are basically 100% waterproof. But there's a catch. The PTFE laminate (or a PU coating, depending on the manufacturer) is extremely fragile, and must be backed by a standard fabric such as polyester or nylon. And so the face fabric is coated with a DWR (durable water repellent) that makes rain drops bead up on the surface. If the rain drops were to soak through the face fabric, they create a later of water between the coating/laminate and the outside ambient air. This means your jacket stops breathing and you become soaked in your own perspiration. DWR's are NOT permanent and must be looked after. Putting your jacket in the clothes dryer on medium-high heat for a couple of minutes every few months will revive and redistribute the DWR along the face fabric. And once a year or so you should probably re-proof a WPB jacket with a commercial wash in or spray on jacket.
Alright, there's how the fabrics work and if I were you, I'd go for a WPB jacket. You'll stay drier!
Cheers,
Adam