One con is that your details might be shared with other agents and companies and you'll start receiving too many calls selling you cards which you already have, asking you to send docs over WhatsApp, etc.
i prefer online and only if you need to apply certain card apply via branch not agent cause i have heard agent at petrol giving easy approval of cc, if any mistake is done you need to chase and get it done and this isn't a easy feat. so other than card like magnus where chance of approval is high or relatively easy cause of C2C via branch if not applicable apply via online vs agent
Pro: Sometimes paid cards will be LTF with some DSAs due to some spl campaigns
Con: Data and docs which we share to them on email/wup will be saved by them which we dont have control (only come to know when misuse happened)