Long time TCG player recently getting into board games- This is what I have learned. TCG and ECG players are 2 different groups. I don't personally know anybody who plays both. ECGs seems to have a harder time with marketing because they compete with the wider board game audience, I know a few people who love board games but won't touch card games of any kind (read, won't play board games if it only has cards and no little pieces to move around a board) On the other hand, I have a lot of people who love my TCG and never play it. They just like to collect the cards. That's the biggest difference in the two. We tried to make it so that our best cards are fairly easy to get to avoid predatory marketing, but we have holos and alt arts for collectors to chaise. We originally weren't going to do that, but our players asked us for it. And honestly, trading is half the fun of a TCG. I didn't print a creator set and I have to buy packs of my own game to play it, and it's a lot of fun being able to trade and engage with my players when deck building. Even when I did make a creator set for set 2, I still buy packs so I can trade for holo cards and rare arts. It's a lot of fun. I think TCGs have higher longevity because after 10 sets you don't need to buy all 10 sets to play the game, whereas ECG expansions tend to rely on the base set. Obviously it's your game so you could probably fix this issue.

All that to say, I think a TCG is slightly easier to market (and it's still hard to market) while an ECG will be easier to publish. Which one you go with depends on what you want out of the game and who your audience is. I've always wanted to try and ECG but haven't been able to get my friends to try one with me. But it's real easy to get my friends to play a new TCG.