Blue had Victreebel which is the best grass type behind Venusaur (Exeggutor is mid game and is really slow to lvl so less useful for a run) and Victreebel's base 70 Speed gives Razor Leaf a 99.9% chance of landing a critical hit.

Also Meowth lets you farm money really easily which gives access to TMs.

Red has Arcanine as a standout but good fire types aren’t hard to come by and Scyther… but having the best bug type isn’t really doing anything.

Honestly I prefer Blue’s exclusives.