I believe there is a big difference between a shooting head system and a sink tip system although the terminology seems to be melding.
IMHO, shooting head systems are primarily built to gain casting distance; control of the fly is a secondary consideration. This is very useful for the salt flats where sight casting to schooling fish is the norm. I use a shooting head system on my 6-wt for Silvers and Cutthroat while wading the shores of Puget Sound. I believe its usefulness in fly fishing the rivers here in Washington are minimal, however.
Sink tip systems offer the primary benefit of getting the fly down to the bottom under varying stream flows and still maintain control of the drift. Changing the weight of the first 15' or so with ease as conditions dictate provides flexibility. This is very useful fishing our PNW rivers varying depths and strong currents challenge the fly fisher. The secondary benefit is the ability to gain distance once you've re-educated yourself on the techniques of the cast.
Its extremely difficult, if not impossible, to control the drift of a fly with a shooting head system since the diameter of a floating shooting line is so small. Also, the shooting lines that I've used (Amnesia, Orvis' Hy-Flote) become rats nets in cold weather; not something you need when winter steelheading.
I made the switch to a Rio Versitip system on my 8-wt 3 years ago. I've since cut a Deep Water Express resulting in the addition of two additional sinking tips to the system. The system does everything I could possibly want under any conditions. Building your own system from a weight forward floating line could be the cost effective alternative to the multi-tip systems now on the market.
An excellent primer with step-by-step instructions on building shooting heads can be found by Martin Joergensen on his Global Fly Fisher site at
http://www.globalflyfisher.com. -------
Fly Flinger
"...Release All Wild Steelhead..."