Whether MBLD or multiblind chess is more impressive is entirely subjective. I have not tried blindfold chess and am only a mediocre player, and my frame of reference is to compare what I know about playing sighted chess to what I know about MBLD.
As Ben said, one fundamental difference is that MBLD is static. It's a straightforward case of encode, memorise, then execute blindfolded. The skills that lead to impressive results are memory techniques and speed, execution method and speed, time management, and concentration/focus, as a single lapse can be fatal.
Blindfold chess to me is almost entirely different. There's nothing to memo at the start. Each game evolves dynamically. As the article points out, tracking the position of each game may be helped by patterns and knowing the history of how the position was reached, and is not just a case of encoding and recalling individual piece positions (like MBLD). Plus, I would imagine, the player would also need to recall plans, strategies, risks and options they had already thought through, including their assessments of what the opponent is up to.
I would guess that for an individual game, it would be relatively easy for an experienced player to play blindfolded. What impressed me about this guy was playing 48 at once, especially since the effort to do so had to be sustained for over 18 hours, and he still won 35 of the games. And it's a record that stood since the 1940s until recently, so clearly not easy
.
