What is more reliable - proxy or VPN?

Question

VPN

Registered on a forum where you can not have two accounts. I want to register a second one.
I noticed that if I use a VPN, then when I open the browser, I need to wait a couple of seconds for the VPN extension to turn on, and then only the IP will change. Is it the same with a proxy, or does it turn on immediately after opening the browser?
I also noticed that the VPN sometimes does not work. Do proxies have stability issues?
And is a proxy or VPN + a different user agent enough for anonymity on the forum?