Starting with the Kerlink Wirnet Station default antenna because I was really impressed by how well this one looks and it inspired me to start this thread.
We see an S11 of -24.3dB at 871MHz. Nice and sharp valley, so a narrow bandwidth around 868MHz. This is a really good example of what you want in a LoRa antenna and this is most likely the reason why Kerlink gateways perform so well.
Conclusion
I would definitely use this antenna on outdoor gateways - if I can find them for sale anywhere.