My boat is only 14ft long, but I really like my Smart Tabs. The advantage over the home made version is the automatic actuator. I don't have to adjust the tabs while under way. They are down all the way when starting and they move up as the boat planes and gathers speed. Combined with proper weight distribution the tabs work great.
Doel fins either require a lot of trim adjustment or you end up with the outboard in a setting that is good for starts and not so great for at speed running. I got tired of constantly changing my trim or paying the performance penalty. Those fins also catch kelp like mad! My Doel fin is languishing in the spare parts box and I don't miss it.