The performance of my network is certainly not terrible when connected to the VPN. Download speed is not noticeably affected and my ping to quake servers (I run VPN all the time, even while gaming) is often lower with the VPN connected.
Regarding your 'why is it more secure' question - because I live in the UK where the government and a myriad of its approved bodies are now allowed to look at user traffic and see my IP and what websites I've visited. I don't have to worry about that now - although yes I need to trust that PIA really are not logging.
The problem with "no logging" policy is you cannot verify it. They can log if they 1) want to 2) mistakenly do so 3) while claiming they really don't 4) are obliged to by (secret) court order (with whatever collateral damage). Its also not anonymous (e.g. correlation attacks). So it seems to be just snake oil to me. I'd rather depend on something like Tor.
Tor is way more secure and anonymous of course, but not at all practical for high bandwidth / low latency applications. Yes you need to trust the VPN that they don't log (your points 1-3). If you trust them not to log, then there is nothing they can reveal under court order (your point 4). It's not snake oil if it does what the seller says it does.
Yeah, that's why I use a VPN; for BitTorrent solely. Which here falls under private law; not criminal law. So the equiv of the RIAA cannot do the correlation attacks whereas (the equiv of) 3 letter agencies can. But the latter don't do private law cases.
I also download over Usenet, over TLS. Its basically impossible to catch those who download over Usenet for copyright infringement since its again private law, and they don't have the power to sniff my ISP's network (though they'd also see encrypted data flowing from a Usenet server).
Regarding your 'why is it more secure' question - because I live in the UK where the government and a myriad of its approved bodies are now allowed to look at user traffic and see my IP and what websites I've visited. I don't have to worry about that now - although yes I need to trust that PIA really are not logging.