Both are fine knives and whether one is better than the other is all personal preference. Both fit my hand just fine and, as long as they're sharp, they'll both cut up boxes just fine. I've never cut up a box with a Para 3 and thought, dang I wish I would've grabbed a Delica because it's thinner blade stock would've sliced this cardboard better. The Delicas do slice through cardboard well but the Para 3s do a fine job too.
To the OP I say don't overthink it. You mention you had a Delica before. If you want to try something new then give the Para 3 a try. If you liked the Delica and want to replace it then go with a Delica. Either one will serve you well
Of all the things I've lost I miss my mind the most!