Not having either davits or arch I have made the same consideration.
I know of boats who have davits with solar panels
and they seem quite happy and there is an added benefit that the the panels
are less likely to have shadows from your rigging
. However having a windvane
may interfere with launching your dinghy
and you dinghy
may interfere with access to the windvane.
I personally like the idea of an arch for solar because they are out of the way and less likely to be damaged when docking
. However, that location would tend to have greater risk of shadow, which would reduce your panel efficiency. Cost wise, davits are about the same as an arch and approvide muliple uses.
It was recommended to me that any windgenerator should be on it's own pole due to vibration. Having an arch my interfere with having a windgen.
In my case, I would probably go with davits when I upgrade.