Another subject over which we had considerable debate was whether to get a wind generator, solar panels or both. In the end we opted for a wind generator, partly because we managed to get a secondhand one cheaply, and partly because, in any event, they seem to give more power for the money. Our Wind Generator is a Rutland. This is less elegant than some others, but it gives a good output without sounding like a helicopter taking off. It also operates in much lighter breezes than most other makes - it probably isn't doing a lot, but psychologically it's good.
We had to have a mounting pole fabricated for the generator, with supporting poles and flanges to mount to the deck. This cost as much as the secondhand generator. I also bought and fitted a voltage regulator and charge splitter, so that the generator could be left connected and running all the time, without any risk of damaging the batteries from overcharging. It's good to be able to go away and leave the boat, for days or months, and come back knowing that the batteries will be fully charged.
We have spoken to several people with solar panels, and many claim that after a few years their performance deteriorates significantly.
If you have the space and the money, a small petrol generator would be a useful thing to carry on board. It would be useful for power tools, and also as a way of recharging your main batteries if they ever get too flat to start the main engine (or if it's not working).
You can, of course, rely on your main engine for all your generating requirements. We're glad we didn't. It's not just that the Rutland provided us with some power when the engine was broken. It's also annoying, to yourselves and to others, to have to run your engine regularly in an anchorage. If your engine is your only source of power, you should maybe consider fitting a "smart" regulator or switchable regulator bypass, and maybe a larger or second alternator.