Both?
I like that you have to unlock commands from the Dream Eater's ability link because it gives me a good excuse to pet them and play with them(I like that they're unbelievably cute). Also, it makes obtaining abilities much more challenging and you end up spending more time playing. Thing is, the only commands that I'd like to obtain from the Ability Link are the commands like Once More, Leaf Bracer and other types of abilities.
When it comes to actual offensive commands, I prefer command melding because less research is actually required if you want to make a certain command. For example, when I played DDD, I obtained Blizzard, and when I visited the Moogle shop, I saw that they were selling Strike Raid. I got overexcited and bought it only to remember that I couldn't meld them together to make my favorite command(Blizzard Raid). In BBS, to get a command like Blizzard Raid, you only have to use simple logic. Blizzard+Raid= Blizzard Raid. But in DDD, you have to figure out which Spirit has that command in their ability link and how to get to that disposition. Also, I somehow feel that it's easier to get creative with command melding. I mean, yeah, the commands you can get are specific, but still, it makes me think "OH!! I want to zap my enemies when I do strike raid! Therefore I will make thunder raid!". As for obtaining commands via Commands Board, that one requires a lot of strategy and luck. I had such a hard time getting some commands in BBS because the dice didn't roll the way I needed it. So for the next game/s, I hope there's no Command Board or anything like it.
So in the next game, assuming there are Dream Eaters(which I highly doubt) or at least an ability link, I'd like that the commands obtained are only support abilities or stuff like special blocking. And if there's command melding, then yay. Command board, no.