Ablative is the way to go...I never heard that fast boat theory before.
You should never have to sand...if you do apply it right the first time
It works well from what I have seen. Hard paint is there forever, long after the antifoulant agent has leached out. This is how you get a big buildup of worthless bottom paint. Ablative wears off over time and can last for several seasons.
There was a great test of antifoulant bottom paints that ran a 9 month test both in FLA and in CT. (Powerboat review) The results were basically that some of the $80/gal paints with 40% CU worked better then some of the $130/gal paints with 70% CU. The bottom line was West Marines ablative (about 80 bucks) was one of the top pics. Also they determined that NONE of the slime agents work that well and added a lot of cost to the gallon of paint. They looked at hard and ablative. Most worked pretty well (some better then others)in fact one reviewer said that he would put any of the paints on his boat because most were very effective. I think there is another test planned too.