Katahdin!

Yes, so I'd say that the best style of mountains is whatever is the most clear and useful for what you want to use the map for. If you're intending it to be used for specific route determination, then a full out topo map with relief shading would be the way I'd go. If you don't need to know the elevations you could forgo the topo contour lines. If you want to give a pictorial representation of the landscape--maybe show how jagged or smooth a mountain range is--a bird's eye or isometric angle might better suit your needs. What did you have in mind?