Jin, I love ya bro. You're a fun guy to play with and chat with. I'm just saying this because I'm going to have to disagree with you here.

I could do it with a group of friends, but when I want to an experience party I like to do it with different people to make even more in-game friends.
I played FFXI for 4 years. I was a WHM and EXP Partied every day, trying to be the best WHM I could.

Despite this, I can't recall any exp PUG I was in where people said, "Hey, you're a good WHM. Let's be friends and play together more often!"

Nor was I ever invited to an endgame linkshell for my grinding efforts. Most I ever got was an, "Oh hey, you're that WHM I partied with the other day, I think. Yeah... Sorry I only really remember people if they suck at their jobs."

It was also the case in XI that level difference meant you couldn't party with someone anymore. So if you played at a different pace of your friends, even if you friended them they wouldn't be able to EXP with you again due to level difference. (Level sync solved some of this, but not all. Generally, if everyone was too high for Colibri groups, they went and did their own things instead)

My point being - Whether it's dungeon content finder or EXP Party grinding, You don't necessarily make friends via these methods. More often than not, you're either already part of a social group or you insert yourself into a linkshell/guild as soon as you can.

You make friends by being a socially amiable person, and by going out of your way to help others. This is true in any social interaction, regardless of the game. Doesn't matter if it's EXP grinding or dungeon raiding.

So please stop trying to use this as an argument for EXP party Grinding vs solo quest content.