Tie both - you never know what the river might throw at you.
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Ab,
I tie and fish flies that cover all the stages in the lifecycle of a Caddis fly namely Larva, Pupa and Adult and I focus on very specific triggers. Match the species in size, colour and profile and fish them at the correct time and place in the river with the correct movements. Already 6 factors to consider. Wait here comes a 7th...
Something that has become very important in pressured water is the texture of material used. Sometimes they don't mind hard stuff like wire or v-rib and other days they prefer things like dubbings,foam or biots i.e much softer which CAN give you that extra milli second to set the hook before spitting it out. If they refuse the one, bet on it that they might prefer another and so on. The 8th trigger could be something flashy or weird incorporated into your natural pattern.Options,options,options! ;) :D
To get back to your Rockworm (mostly Caddis larva) question try both, play around but take caution against stagnating on things like V-rib.
I value any advice, even better when two great tyers give the same advice.