I've had a fair bit of experience with pond liners, and all of it has been outdoors, subject to muddy conditions and the vagaries of the Scottish weather.
Butyl rubber liners are very resistant to being punctured and have excellent elasticity, being able to stretch surprisingly far before tearing. If they get muddy, the clay particles tend to bond to it and can't be cleaned off completely, which makes it more difficult to get butyl joining tape to stick to it, but a heat gun can be used to heat the liner before applying the tape, which results in a better bond. They're very heavy, which can make handling them difficult.
Polypropylene is much less elastic than butyl rubber, tears more easily and is more easily punctured, but it's still strong enough for most purposes. Just be careful when walking on it with hard-soled boots, since they can tear it if they catch it the wrong way. While butyl rubber tends to stretch over the bottom of the pond to form a close-fitting, smooth membrane that traces whatever terrain is below it, polypropylene tends to form large, prominent crinkles wherever the shape of the pond causes excess material to bunch up, which provides shelter for animals, but can look odd and unsightly unless carefully adjusted for aesthetics as the pond is being filled. It's easy to clean if it gets dirty and doesn't suffer from the clay problem that affects butyl rubber, and butyl joining tape has no problem bonding to it. The weight it intermediate between butyl rubber and PVC.
PVC is much the same as polypropylene, but lighter, which makes handling easier, perhaps a bit less durable, gets stiff at low temperatures and can possibly be solvent welded, though I've never tried that. Butyl joining tape bonds to it just as well as it bonds to polypropylene. PVC pond liner is easiest to work with in direct sunlight on a warm day, as the heat makes the liner much more flexible.
In addition to butyl joining tape, I've found that Everbuild Weathermate sealant is compatible with all three materials, as well as with butyl joining tape, and I often apply a thin layer of Weathermate over and around joining tape to seal any small holes or gaps caused by airbubbles. I don't recommend using silicone; it won't stick, and then nothing else will stick after the silicone has been applied.
