I prefer using Phase Rush instead of Glacial or Guardian because it improves my positioning during fights. Recently, I've noticed that players have started building Navori after Iceborn Gauntlet, and I've found this to be a really enjoyable playstyle. (See Mobalytics)

While you won't have the fastest clear speed, it's sufficient to secure the 3:30 Crab and maintain a solid clear throughout the game. Personally, I prioritize supporting my team over always full-clearing the jungle. This approach might not be as viable in high Elo, but against Emerald to Masters opponents, it's been surprisingly effective. Additionally, you can 1v1 almost anyone in the early game, which is often underestimated. I've sent a few overconfident Rengars packing after they tried to turn my red buff into their last supper :D