I dont think there is more of a debatable issue in the game right now than the value of 2013 cards. Even more debatable is whether its in everyone’s best interest to trade inserts from 2014 for top cards from 2013. Im going to try to offer my opinion on the matter, but please realize there are many different ones.
Personally, the only 2013 cards I have in my collection that matter to me, are the inserts from my favorite team. Its kind of counterproductive to have the inserts in some cases, because default filters prevent people from seeing them unless they are truly trying to seek them out.
Because 2013 cards no longer score, the cards are worthless to the gameplay, but collectors (especially ones that were around then), still value a lot of the 2013 cards more than the 2014. Mystery Andrew McCutchen, Bryce Harper Sig, Hank Aaron RC, and Mariano Rivera’s RC cards are still sought after in a lot of ways, but you have to find the right person.
To further highlight how I feel about 2013, I do not seek them out one bit. If they are offered in trades for any card of mine that has even remote value, I will usually turn it down. As a person who is full of vanity and wants my collection to be seen, its hard to trade a card that looks good on my card sheet for one that will never come up.
It should also be quite clear that the 2014 cards werent as design friendly as a lot of the awesome inserts from 2014. The game has evolved, and its evident that the design and look to the newer cards are much better. If you like the 2013 cards, more power to you, its whatever you feel is a target for your collection.
I think in terms of rarity the 12/13 cards will prove much rarer than their 14 counter parts. As far as collectibility the cutch and Kershaw bases are very desirable and very hard to get in trade. Before the release of 14s owners were demanding sigs for them. Regarding inserts I would say the trout silver slugger is the most desirable and most difficult to trade for. The 2013 trout sig is probably most in demand of all 2013 cards because of the trout collection reward.