So if you did NOT enter your 1095-A in prior years and you think you would have qualified for the Premium Tax Credit, you may want to amend.
https://ttlc.intuit.com/questions/1894381-how-to-amend-change-or-correct-a-return-you-already-filed
As for your question for the Pros and Cons:
Neutral: If the number of people on your tax return is the same as what you told the Marketplace, and your actual income is similar to what you told the Marketplace, the "net result" would be the same. It would not matter if you received Advance credits to reduce your monthly insurance cost, or if you take it all on the tax return. The end result would be the same.
Pros for taking the Advance credit to reduce your monthly payments: If your actual income is significantly different than what you told the Marketplace, it often better to have taken the Advance credit. That is for two reasons: (a) If your income falls too low to qualify for the credit, taking Advance credit will still qualify you for the credit, and (b) If your income is higher, your repayment is sometimes limited.
Cons for taking the Advance credit to reduce your monthly payments: If your actual income is significantly higher than what you told the Marketplace (or you have fewer people on your tax return), you would need to repay part or all of the Advance credit. Although the "net result" would be the same either way, you would need to be prepared to make the repayment when you file your tax return.
