Recently I was served with a civil action complaint from a credit card that I am six months delinquent on. The credit card company is sueing me in the PA Court of Common Pleas for the amount owed on the account. My husband has the same card, also six months delinquent, account was opend around the same time, and he owes more on his account than I do, and his account went to a collection agency. I would like to know why or how credit card companies decide who gets sued and who gets sent to collections.

Depends on which collection supervisor may have the account,

Depends on companies current policy, ( did they just do a get tough?)

And in your case if they are not getting the money from him, they may decide just if his collection is not working yours will not either?

Many things go into these decisions.
They look at the amount, and they look at the odds that they will be able to collect it.
When they assign to an agency, they are normally giving up at least half of what is still owed.
They would only do this if they feel it will be difficult to collect even if they obtain a judgment.
If they feel confident that once the judgment is obtained, they can collect it, then they will be more likely to keep the debt and collect all of it themselves instead of giving up half of it.
Chances are they have looked at your assets, your employment situation, and have decided that they can probably get all that is owed to them on your account.

Life is not always fair, this is probably a good example of that.

Could also be the result of a coin flip :)

Seriously, you have gotten good advice here. The most likely reasons are different account managers and someone believing a different level of collections is needed.