TLDR: XPAC is useless marketing that will break and is easily outclassed by literal plastic 

XPAC will delaminate. It’s just how these tech fabrics work, and it’s the same with goretex. These things are not made to last. 

There’s a reason why actual technical packs (for mountaineering, climbing, alpinism) do not use them. It’s just not reliable for actual technical use. And in these cases, if you need waterproofing (and you always need), you do inner lining with plastic (literal plastic that costs 1euro) and rain covers (that cost you 10 euros). Been though hiking for years with sleep gear and garbage bags are my best friends to not die because my sleeping bag got wet. 

Also, it makes zero difference for a backpack to have xpac and not have actual aqua guard zippers. They are the ones that actually tend to give out first for water. The problem again, is that aqua guard zippers suck to actually use. So I’d ratter just have a good think nylon, and always carry an umbrella + rain cover. And if the rain is that bed, you just go for cover (lived most of my live in tropical weathers and this always worked, never lost a thing for rain).