I think braids doesn't aid in hair growth, I feel that is somewhat of a camouflage (kind of hard to explain).
Honestly speaking, I think I would have acquired the same amount of growth from wearing braids/weaves vs.. wearing my natural hair, however, I feel that my hair would have been more dense if I would have grown it out naturally. The only reason why I attest this is, when I got my first relaxer after completely removing hair extensions from wearing over an extended time, when I would feel into my scalp I could feel little sharp hairs sticky through. Now that I'm wearing my natural hair out, I don't have the sensation any longer. But I noticed that feeling each and every time I took out my braids. However, I always acquired length without a doubt.
I'm not totally against weaves and braids, but I feel from my past experiences that when putting in a weave or braids, your hair should be in the healthiest condition and you should NOT wear over extended periods.
Another effect that I experienced with weaves and braids were traction alopecia. Now, I didn't suffer from the traction alopecia because the braids were too tight, it was due to the braids twisting and moving around. When I would remove the braids, I would notice in areas especially my crown, many strands of hair attached to the braid with the hair follicle attached thus resulting in less density in that area. However, in the back I maybe not have experienced any loss and gained hair length, but at the crowd, I'm two steps back from where I started. I hope this is making sense.
The weight of the braids was also a factor as well especially while their wet, if you have synthetic or human hair. It's very heavy when wet and puts excessive stress on the hair itself and follicle.
With weaves I suggest net weave but that is the less amount of stress throughout your hair, however, in order to sew the track down you require a base and that's usually a cornrow around your entire scalp. Mind you, you have the entire weave and its pressures basically concentrating on this one section. So when washing, this area will be stressed more than the area that the net isn't sewn down to.
If you decide to do the traditional weave, when your looping that thread and needle through the plaits, the cotton is rubbing against directly your hair strands. Now, if were hesitant to wear our hair down on cotton and wool clothing for fear that our hair will come out, I applied the same theory to the thread. Additionally, if you use Yaki hair for weave, no matter how great of a brand you purchase 99% of yaki hair gets bushy at the base of the neck over time. Combing that constantly, even though you feel like its not much, it is some sort of stress to your natural hair.
Pheww.....sorry for the long winded reply...However, I feel I will weave braids or weave to attain a certain look that I would like and probably wouldn't keep it in no longer than one month. For healthy hair growth, I opt and I find with my hair its better growing out my hair naturally (relaxed), I'm able to retain more density and lessen the need for trims. But your right Kit Kat, everyone's hair may not react as mine did. But I felt the need for those who've worn braids/weaves for short periods and/or those who've never worn them to know what wearing them over extended periods can do to the hair. This is why I feel a lot of celebrities after a while stop wearing weaves because of the effects, take Beyonce, Ashanti, Mary J. Blige, Lil Kim for example. I'm sure they probably experienced the ill effects of wearing them soo often and soo much as I did. I was almost two steps from having to wear wigs, but I stopped it and got in to healthy hair care and my hair never looked this good, been this healthy and strong.