I've never found leger stops to cause actual line breakage, although they can cause visible distortion - i.e crushing or flattening of the line. Provided the cross sectional area of the line at that point is the same as the unflattened line elsewhere the breaking strain should be the same. Then again, I only use Maxima or Sundridge Green Force nylon; problems may well arise with pre-stretched nylon, fluorocarbon or braid.
Incidentally, I still use pieces of biro tube plugged with cocktail stick as stops when carp fising, which are even better than plastic stops as the wood softens and swells when wet, giving a firm grip on the line without damaging it. Two quarter inch pieces of tube with a half-inch piece of wood is about right; for added security I take a couple of turns around the plug with the line.
A swivel and bead should of course be used where leads in excess of one ounce are required and long casting is necesary, as no ordinary stop can withstand the forces applied in a powerful cast.
For barbel my set-up is even simpler than Sean's; two float rubbers go on the line first, followed by a link swivel with an eye large enough to pass over the eye of a size 4 Drennan Super Specialist. Then I tie the hook and pinch a swan shot on to act as a stop. That's it. I can use the swivel to attach any size lead or feeder I require, I can adjust the length of tail easily and I can remove the shot and swivel if I want to use a knob of plasticene for a rolling bait. The float rubbers are there should a spot of trotting be called for.
The only time I have to remove the hook is to change to a larger or smaller one.