Hi Andy

I had the same dilemma at the start of the year.
I ended up going with the midsize bag after much debate!
It’s been great throughout the summer and can handle a quick shower.
However, I also live in Scotland and the bag really isn’t great in ‘proper’ rain.
Unfortunately everything gets very wet
I’m thinking about the stay dry premium bag for the winter. The stay dry 15 seems to be good and stands up well in the wet so hopefully the premium one does too!
If staying dry is no1 priority then I’d maybe avoid.
Other than keeping stuff dry the bag is great!!

Hope that helps!
Cheers

Recommend you go with the StaDry bags for best results against the weather you guys have over there. If you can the Drihood Towel Bag Hood, I recommend one of those. I use it to cover my clubs. I ride a cart 100% of the time due to hips and back and the cart has a drop down cover on the back to keep my mid size tour bag dry. If it rains hard enough to get the bag wet, they close the course due to flooding. When the geese hide from the rain, you know it is time to leave the course......

I recommend the Stadry bag. I have had mine for almost two years and it is easily the best golf bag I have ever had, it is incredibly durable and protects my equipment from the most brutal rain.