I fish for pike almost exclusively on still water/lakes and I have abandoned the "weed gaurd" idea altogether. It's more trouble to tie, it often fouls the tails of flies, spring type guards (like the ones you are talking about) often open while casting, other styles (looped mono etc.) often move and after all the efforts of not getting stuck in weeds, I still get stuck.
So I've not much use for guards.
Most importantly, I find my catches mostly come from areas close to weed beds but seldom from the bed itself. So casting accuracy, fly design and line selection seem to be a better investment than guards.
Pete AKA Frenchcreek from Calgary