I have the Current Sat Plus on an ADA 60-P tank. The light is suspended about 2 inches above the top of the tank, and the tank has probably 3" of ADA substrate. I think it's been on that tank for about 3 full weeks now. My fissiden mosses are loving the light, I have a really good green biofilm on the 3 edges of the tank- which I want because I am keeping shrimp in it. The different lighting options are really pretty cool. After you play with them, you probably find your favorite and stick with it. However, once I have shrimp in the tank, I might do the simulated cloudy day where the light intensity fluctuates/cycles around.
For your 55 gal, it might be stretching it a bit. You're probably just on the edge of low light getting down that far. If it were me, I'd probably go with the Finnex for that tank, and if you find that it is a bit too much light, get some risers to lift the light up, shorten your photo period, etc. I think toning down a light is easier than having to make up for not enough. I actually have both brands of lights on different tanks, and like them for different reasons. On my shrimp livestock tanks where I don't have the depth to worry about, I get the Current lights because I like the light cycle features and the color options. On my mainly planted tanks, I like the Finnex because the tanks are deeper, and I have the extra pop in the PAR that I can deal with if it is too much light.