Nuge,
The Shockwaves use a rubber band as well.......really though, I have been using rubber band style mechs since 1997 and haven' t had a single one break or fail in anyway.
If you get a package of Steelheads (Made by Rocket Aeroheads) probably the best penetrating 3 blade mech on the market and they come with a bunch of replacement bands if you get leary of the ones on the head at the time. There are a ton of guys who swear by them.
Its easy to see a dry rotted band, and nothing to replace them periodically.
Plus these styles open quicker.

As far as the Snyper goes I believe guys were getting rather good entrance and exit holes? They are alittle different shaped, sort of oval, but plenty big enough.