I bought my metal clips and roller jaws around the same time I think. I tried both but didn't quite know what to do with either. I clipped my curls with the metal clips like in the Curly Girl Handbook (or at least what I thought it was to the best of my deduction) but didn't find they had any hold. They'd flop over and snag on the hair, like you said. However I was able to get better volume and placement of the curl a couple of times but results weren't consistent and I'm lazy so I just gave up. (I much preferred bobby pins in dry hair.) And then the roller ones I've tried several ways. They don't work for me at all with wet hair. Too big and cumbersome. So they don't sit up when the hair is wet. Then dry I never got the hang of either. The few times I tried I had to pull the top of my hair back afterwards. Actually Skorpio said something about them that resonated with me. She said that if you're more of a wavy curly and have less elasticity, the roller jaws pull out the curl at the root. Looking back I think that might be what was happening with me and the clamps although I haven't given up on them altogether. I'm sure I'll find some use for them. But I digress. the reason why cross clipping works so well for me is not only does it boost root volume/curl, it's the fact that one clip helps uphold the other very tight. To the point that I can flip my hair upside down when diffusing and not have either of them fall out. I realize I have thick hair and that might be why the clips are staying in but when I used just one clip it'd hardly stay at all. And they'd tangle. With cross clipping if you grab the head of each clip and release tension at the same time, sliding out slowly, you don't get scalped. Well at least I don't.
3A - C, HP, ME, HD. (Coarse, High Porosity, Medium Elasticity, High Density.)

CG since Nov. 2012

Poos: SM Moisture Retention + Yucca Baobab, TJ's Tea Tree Tingle
Condish: TJ 'sTea Tree Tingle*, SM Moisture Retention* + Curl & Shine + Yucca Baobab, Yes to Blueberries
Stylers: KCKT*, SM Curl Enhancing Smoothie* + Curl & Style Milk*, KCCC*, FSG*, CJ Pattern Pusha, Curl Keeper
Sealers: Jojoba* or Grapeseed* oil

* = HG