I'd say: fell shoes hold the foot tighter, have lower profile soles (i.e., barely any cushioning), have more grip in the way of proper studs, are probably lighter and usually less comfortable. So Inov8 Mudclaws, Mudrocs and Xtalons, Walshes, Montrails = fell; most of the rest = trail.
and there's a few that could be described as either
Not all fell shoes are durable either - the racier models of Walshes and Inov8s have both come in for some stick for being the opposite ...
For summat like the fellsman I'd personally be very much looking at the trail end of things, with a bit of comfort and cushioning. You won't be leaping down many steep descents at top speed after all.