If do you not arrive before 45 min early OR if you do and already find a lengthy line, I highly recommend the main gate. The entrance from GCH only has 2 turnstiles whereas the main gate has somewhere in the 20’s so MUCH more capacity.
If you are early in line for GCH though, no reason not to use that fantastic entrance to save some steps. A little earlier this year, DCA changed it’s RD procedures for that part of the park & now once they start letting guests in (as early as 30 min prior to park opening) you’ll be able to line up at a rope all the way at The Little Mermaid Ride- to position for Toy Story Midway Mania or another possible route to Carsland- pretty equidistant to the main entrance. With the rope that far up you’ll be able to walk all of the Grizzly peak including starting to form a line for Soarin (won’t be let into the queue, but people start making a nice line from what I’ve seen), and pulling WOC FPs (kiosks located right next to the Little Mermaid attraction) . Since Grizzly Peak borders the the hub, you’d also be able to walk easily to where the ropes for Hollywood Land (where GotG) and center of the park (up towards Carsland) will be stationed. Also, Fiddler, Fifer & Practical Cafe in that hub is a Starbucks which has been one of our favorites to eat while waiting for DCA rope drop.