I have carried both, it depends on what I am wearing. The speed strips are infinitely more concealable unless you are wearing a jacket or something with loose pockets. A speed strip will fit perfectly in the little pocket on a pair of jeans. When I carry speed loaders they are the Safariland Comp I or Comp II variety for my .38 snubby and the HKS type for my .45LC revolver.
An armed society is a polite society.