I think the type of knife and intended use determines whether guarded or guardless is most appropriate. I like little "utility" knives without a guard for 99% of my use.
On the other hand, when I was living in Germany I was making knives and selling them to a gun maker who then resold them in his shop. I brought him the prettiest little knife without a guard. He refused to buy it and said it was dangerous. This may be an urban legend or not, but this guy normally didn't lie or exaggerate. He said one of his customers was boar hunting; shot a boar and it appeared dead when he approached it. He put his gun down, got his knife out and started to roll the pig over. It suddenly came to life and started kicking and thrashing. He tried to stab it behind the front leg, hit a rib and his hand slid down the blade and he nearly amputated a finger.
I think you can make a solid case for either design if it all fits as a package - visually and according to its use.