For me it's not a psychological profile thing, at least I don't think it is.
I have Empire, Warriors of Chaos, Tomb Kings, and just a little bit of a Daemons army. At one time I had Bretonnians, they were my first in fact. All very different armies that play differently. Currently I'd say Empire is my favorite.
For 40k, I have Eldar, IG, and I suspect I'll get Dark Eldar at some point. The Eldar are two fast finesse armies, but the IG isn't. Eldar were my first 40k army. Eldar by far are my favorite 40k race/army.
So just basing it on first armies, Eldar have a different play style than Bretonnians do, so I don't think it is a psychological profile thing. Sure there has to be something that draws you to an army or turns you off another. Who knows? Of course, I'm a person who gets more than one army for every game I play, so maybe that in and of itself is part of the psychological profile?