Nobody said solids modeling wasn't great. If all you need is a pencil sketch, do it. If the job is a long one, that ties in with other structure, you had better not throw good money after bad. So start drawing it in cad. If you need to dazzle some fool, you would be best in 3d rendering, but most times the 3d line drawing (on computer)does all I need to communicate with a customer, or check an installation, pull off items for fabrication etc. If I have a bent section,(like skew ductwork) I'll make it easy on myself and connect the dots, before unfolding it into a flat plate!
The same goes for views. Use traditional views if that works. I'll do a 3d and slap it in the corner so the fitter gets up to speed quicker if it is cost effective (Does it save enough of his time to justify mine?)
Incidentally, CADKEY has a better package that is not write protected anymore. A true 3d.