I didn't care for Martin M600s on either of my non-wood ukuleles (Flight TUS-50, Outdoor Soprano)-- they felt and sounded way too thin, resulting in "plastic" as the overall impression (more than usual).
I now have Freemont Blacks (high tension) on the Flight, Aquila Sugars on the Outdoor. I like the Sugar strings very much, but they are already starting to show signs of wear/fray at specific fret points.
[Objectively, the Outdoor is the worst sounding of all my ukuleles-- the Flight does sound better-- but I prefer the Outdoor's quality
feel to that of the Flight, which I find sorta icky.
I am currently playing the Outdoor more than all other comers, because humidity is way low here right now (even with room and in-case humidifiers) and I have no worries about keeping the Outdoor out, within ready reach-- even when I'm sitting directly in front of a space heater.
]
Thanks much! Here's to the day.
~ S.