Old Whur-whatever is less of a no-brainer compared to Tri-Sword, actually. I can think of a couple of things off the top of my head.
1) If you're worshipping GG, he doesn't like it if you kill popcorn monsters, and converting to GG late after you killed every low level enemy is pointless.
2) Things like Blue Beads, Tikki's Edge, Crusader's Momentum ability requires you to be a bit more smart in leaving popcorn monsters behind so you can take advantage of them.
For Twi-Sword you don't even need to think about those things, you basically play normally which is "kill higher level monsters, get free damage"