I'm sure this is too late, given when this was posted, but thought I'd put in my $0.02.
I did that ride from Toronto through NY/VT/NH/ME, then through NB and PEI to the Cabot Trail back in the latter half of July. I didn't realize the weather was that bad out there - I really lucked out, only about a combined 60 minutes of rain in the entire 12 days I was on the road!
I tell everyone that every single time, don't listen to Google Maps (the Quebec route) - you want to go through the states. You get the experience the Adirondacks, the Appalachians, the White Mountain area in NH (do the Kancamagus Hwy & Bear Notch Rd), and coastal Maine. It's all beautiful and fun as hell to ride. NB was a snoozefest, PEI was pretty but also boring.
I had a great time on the Cabot Trail, but I will agree that for the distance you have to endure to get out there, it's hard to justify. I spent 4 days/3 nights on the trail, but it takes about 20hrs of riding just to get there (which for me is about 3 days).
Once you do get there, it's awesome, as long as you have a few days to take your time exploring. Find a few fun stretches and ride them back and forth a few times. Visit Meat Cove, Ingonish beach, Neil's harbour, etc. Kick off your boots, take off your socks and walk through the ocean a bit. Hike the Skyline Trail, spend an hour just enjoying the view. Visit the coves and climb some rocks. Oh, and enjoy the seafood, of course.
But, if you only have 6 days, that means you'll basically just have time to get out there, ride a quick circuit around, then hightail it back. In my books, that's not really worth it, especially since after Maine, the stretch the NB and parts of NS are pretty dry. If I had 6 days to work with, I'd probably just plan on just heading out to Maine and back, but spending a lot of time exploring the area (lots of roads to ride), maybe drop by Boston, etc.