It's really going to depend on what you like to do. I did not stop at Loch Ness, but drove right it and don't think I missed much. It's a big lake with a monster myth, but we have one of those here where I live so it didn't seem out of the ordinary to me. It was not a recommended stop by the company that did my driving itinerary, they stated it was over-rated and over priced. I think doing it from Edinburgh is going to be a very long day on a bus. Glasgow, however, has many interesting things to see and do, and is fairly easy to get around on by foot, or the HOHO bus. Glasgow will be more about museums, art (Charles Rennie MacIntosh), and architecture (always look up when you are in Glasgow). Keep in mind that when you take some of these tours the cost of certain things is not included. So, you may want to take a boat tour when you get to Loch Ness, but that will most likely be an extra cost to you.