BOTH!
I will generally use a throwline and I have a small bag with two lines ready for deployment, also contains a rubber mallet, binocs, xtra throwballs, keychain biners, lighter, candy bars, and anything else I can squeeze in there. As I leave the truck I grab the bag and I can usually have a line up before the chipper is greased.
But...just yesterday I found myself in a jam with TWO throwlines stuck about 80' up and no other spares. I'm usually pretty good but of course there was a crowd going "Ooh, you make that look so easy". So without missing a beat, I let the groundie waste time with impossibly stuck lines and I quickly tie a thrower's knot and LAUNCH it about 30' to the second branch. Then I begin the tedious but not impossible task of recrotching all the way up to the pencil tips to get me throwballs.
Yes, both are critical for efficient canopy access.