That's sort of a hard question to answer. People are interested in different things for their children, so what they are looking for in education will be different. Of the three listed, Reggio and Montessori share many similarities and are both extremely different from Waldorf.
I think with issues like this, the parents tend to be supportive of a way that they see their child thriving. So people really stand behind what they see as ideal for their child.
With Montessori, parents see the focus that develops, the child's love of academics and seeing it being a part of natural development, the creativity, independence, and the social aspects that come out of being in the program.
With Waldorf, parents tend to love the art, rhythm of things in life (their words...not mine), imagination, and fantasy that comes in life.
With Reggio Emilia, parents tend to love how the teacher can be so creative and resourceful and pull a variety of learning experiences together based off the children's interests.
Unfortunately, the term "traditional education" sort of lumps a lot together, so it's hard to speak about that. Generally speaking, it is teacher-lead classes based off some vague or specific curriculum. There are a million ways to do that and many of them are good...it's just hard to address something that general.
What I see as a good mix is when parents know about their school, the teachers are dedicated and passionate about their teaching, and they work together. I'm obviously partial to Montessori because I see it as the most logical way children learn (and adults....you'd be surprised how many adults finally "get" math after working with the materials for a while). But I'm just as excited to hear when students fit well in a different program.