It can get old very quickly to travel down a peninsula, see a lovely ocean view or lighthouse or quaint town, then travel back up the peninsula to highway one for some miles and then down the next peninsula, and again, and again. That would mean getting off of highway 1 and doing many detours down the peninsulas, to Popham Beach, to Boothbay Harbor, to Pemaquid Point, to Port Clyde. I see from another post you made that you want to travel the most scenic route. There are always major slow downs in Wiscasset and in Camden during those months. In July and August, it can take a long time to travel highway 1 because it carries a lot of tourist traffic. It very much depends on what time of year one is traveling between these two towns. Highway 1 runs inland for much of its length, crossing tidal rivers in small towns. There are few water views because of the very jagged coast of Maine. The other reason people recommend the interstate route is because the so-called "coastal route" isn't really all that coastal. The reason that people recommend the interstate route is because it is faster than going slowly through all the small towns along highway one. It's about 174 miles if you take the interstate to Bangor and then 1A and 3 to Bar Harbor. It's about 154 miles on Highway 1 from Portland to Bar Harbor.