I keep our boat in the water about two years out of three. As you say, it is in many ways safer, and may even be kinder to the hull. Down here is is not always necessary to drain the fresh water system, but I do find the the humidity is a lot higher on the water, making a dehumidifier essential, especially as much of the upholstery can’t be removed. The main concern to me is the possibility of the saildrive prop anodes disappearing but generally they just about hold out.Mine will stay in the safety of the marina over winter, where its safe and reasonably warm, it has done for many years now. My on land storage is inland north east Scotland, where it gets properly cold, and engine damage is likely, even with good attention to winterising. This year was a disaster, with outbuildings collapsing and lots of general damage, so its safer in the relative warmth of the marina. So it stays in the water till March / April /lockdown ish then its home for a clean up and major service. I have recently bought a small yacht, to add to the powerboat, and it really has to stay in the marina, but the plan is to get the antifoul and anodes redone in spring. Both are basically winterised now, with covers on everything and well battomned down, all mooring lines checked and in some cases doubled. I will visit mopre or less weekly and if we get the right spell of weather i will certainly try to get out for some local sailing or fishing.