All of the flies (and jigs) pictured here will, no doubt catch trout.
Having said that, the peeping/peeking caddis is designed to imitate the phase when the larvae and it's case are either dislodged from their attachment to the stream bed, or are intentionally moving from one location to another.
Lafontaine's
Caddisflies describes these activities beautifully. He points out that when they are drifting, they drift with their head in a downward orientation.
When I tie these types of patterns, I like to mimmic that.
Many of the flies (and Shane's jigs) depicted in this thread will drift in the opposite orientation.
The first (top) of nfrechette's flies will drift that way (head down), but his other one won't.
I'm not suggesting that some of the flies pictured here won't work. They will. All of them are tied well. But, I'll bet a bead head gold ribbed hare's ear would fare just as well.
Sometimes I use a bead. Often times I use shot. With the "reverse" tied patterns (caddis head and legs at the bend) I tend to add the shot on a dropper off of the hook bend instead of weighting the leader. First of all, I prefer tight line nymphing and sight nymphing over indy-nymphing or euro-nymphing. Secondly, I usually have a dryfly leader on and am too lazy to change it, so I want to avoid putting shot on the tippet...
When does it matter if you're using a head down peeping/peeking caddis instead of the other flies or a BHGRHE? Probably only when there is a Grannom migration going on just prior to the hatch when the trout are really keyed in on cased caddis.
My $.02
And my flies...