I’ve used these on my hurdy gurdies to great effect, the violin A working as a high G on a 345mm soprano gurdy. As with all Vision strings, the winding is quite delicate so take great care when changing cotton, and ensure you have nicely rounded wheel rims and minimal downward pressure against the wheel.
Honestly I haven’t yet noticed much of a difference between the Vision, Vision Titanium and Titanium Solo strings (at least on a gurdy) so take your pick. Perhaps the Titanium ones are a bit more robust, and the solo ones a bit brighter, but it’s not a huge difference.