I was a boat lift mechanical engineer for hydrohoist. At the time I was one of the most knowledgable people in the world about boat lifts (most of those companies dont "engineer" them). The best device I can give you is "it depends". If your dock has every other "finger" as a metal rail instead of a wooden platform you want a more flimsy cheaper lift. The same goes if your dock gets beat up by waves real bad. I have one slip in shell knob right on the end of needles eye that is a good example of this. It has metal fingers and gets the crap beaten out of it, especially during 4th of july. If your dock meets either of these two requirements i would go with a cheaper boat floater or econo-lift. These two have been around for a long time compared to many of the other companies who throw these things together in their shop in the backyard. These lifts will break. You will need to change out fasteners every few years to tighten it up but no lift can survive long in heavy waves and a more rigid lift can damage a flimsy dock.
If however your dock is in a relativley calm place and is built like a tank (rigid wooden plank fingers, nice platic enclosed styrofoam floats, etc) your best long term bet is a Hydrohoist. An Ultralift in these conditions will last 30 years with virtually no maintenence. You will recoup the extraup front costs because it will last forever.
Sorry it was so long. Im in shell knob so if you give me name and location of your dock i can check it out and tell you for sure which direction is better for you. From a dock and long term financial stanpoint. This goes for anyone on here that needs boatlift advice.