Hi there. I can't comment on the Seacroft end, but I suspect sticking with the towpath to the centre will be the more pleasant route. Going to/from the city centre I sometimes use the A65 as far as Kirkstall, which is faster than the towpath and ok as there is bus and/or cycle lane all the way, you just have to be alert for drivers crossing your path into the side roads.
If you try and draw as straight a line as possible from Rodley to Seacroft you are crossing lots of the main traffic routes into town from the north, which sounds like a pain in the arse. Also, hills.
