To avoid confusion a permanent magnet alternator is any alternator that uses permanent magnets for the field, that includes the axial machines.
I suspect the things you are comparing are radial flux, iron cored alternators.
Are you by any chance looking at small machines suitable for use on boats?. Some of the commercial wind farm machines are permanent magnet radial field, iron cored machines and have outputs in the MW range, not particularly low by your definition.
I think we are talking about direct battery charging machines without electronics in your comparison and it is true that iron cored machines do flatten off to constant current in high winds.
Everything is a compromise, nothing is perfect for any job but wind machines are more of a compromise than most.
For survival in marine environments there are advantages to having everything enclosed and away from the salt spray so I would agree that the radial machine has a big advantage here.
For the rest it is a compromise between cut in wind speed, size ,weight and maximum output. It is always the case that going for good low wind performance really knocks the performance in high winds.
In marine environments the wind speeds tend to be higher and rated power can be at a higher wind speed than on most land sites. You have to choose whether you want any output in winds below 10mph or whether you want higher maximum output power on very windy days. you also have to look at survival during storms. If by marine you mean on a boat then it is not easy to use furling schemes designed for land based machines.
Once you start looking at winds above 30mph, survival is more important than power out unless you are looking at something that only produces power in storms.
You can build small machines with a spectacular output in gales if you optimise the design for that but it will produce nothing most of the time.I can't help thinking from your previous comments that you are looking for incredibly outputs from tiny machines. In reality it is the snake oil brigade that make these claims and no realistic turbine designed for normal wind sites will even get close to these figures.
For marine environments I would look for an enclosed design, that doesn't rule out axial but it won't be in the usual open form.
If you want the best of all worlds then you need to go down the mppt route and the current limiting problem of radial iron cored machines then don't become a limitation and you can extend output up to wind speeds where prop speed becomes the deciding factor. Iron cored machines will never deliver the best low wind performance but if it is for a boat at sea this may be no big factor, if it spends a long time in harbour then it could well be a factor.
There is no perfect solution, just work out the best compromises for your needs.
Flux