Working on primarily boats, we use stranded whenever possible.  Essentially all of our cable runs are patch cords that we've made ourselves and we haven't had any issues over the 10+ years that we've done it this way.

I will say that finding stranded/shielded, cat6 in bulk is impossible. (someone will call me a liar and link a product and probably miss the part about being both shielded and stranded) So we've ended up sticking to cat5e shielded/stranded cable except for products that specifically call for Cat6, then we'll run solid if we must.