Silicone, in my experience, has a lot of bond failure. I can come back to an area where it was applied and the bead will be intact but it will be loose from the substrate. Depending on what type of substrate, it can bond well. A trailer side is not a good substrate.
FWIW, I use a relatively good amount of caulk for work. Most of it is acrylic for good paintability. I use silicone inside, around tubs, sinks, countertops, etc.. I sometimes use urethane and now, polymer caulks outside for typical sealing jobs. IMO, the polymer caulks are best. Geocel makes a few different ones, including Proflex RV. I've been using the 2300 series from them and it is very stout.