If you join some random FC that invited you without even knowing who they are:

Advantages:
1) You'll get the benefit of Company Actions. Most FCs use these and they give all members some benefit, whether that's XP boosts or travel discounts, or any of a number of other perks.
2) You may find friends you can run content together with, or crafters who will help you with gear, or people you can help with their content or gear.

Disadvantages:
None, really. The nearest thing to a disadvantage is that if you make friends there and then later get in a fight with them, you can end up upset by the fight. But that's just the danger of making friends.

For the most part, even a "bad" FC is simply one that isn't doing much that you're interested in. No matter which one you're in, FC chat cannot be any more quiet than when you don't even have an FC at all. So try one, any one, and see who you meet there. If after a while you don't really like that group much, you can leave and try your luck with a different group. It shouldn't take too many tries before you find one you like and can start making friends.