The ‘need’ to fill (with a recovery tank) would be to thus have more coolant volume (assuming then, better cooling efficiency?).  I would also guess, that much like with oil in a larger crankcase capacity, life of the coolant would be extended.  The ‘need’ to NOT fill (no recovery tank) would merely involve the puddle on your garage floor, after the system contents expands when car is parked hot, and the expense of constant replenishment (assuming the system is refilled).
The benefits of enacting a closed system (higher boiling point, less corrosion, etc.) are usually best only with all new components.

A larger volume of coolant would not affect cooling efficiency nor extend coolant life. The use of a recovery tank simply retains the coolant in the system instead of some of it winding up on the ground after a hot shut down. The same can be achieved by leaving expansion space in the upper radiator tank as original. A higher boiling point is achieved by using a higher pressure radiator cap and has nothing to do with the presence or absence of a recovery tank.

Boiling a quart of water on a stove takes longer than boiling a pint of water. Is that what you're referring to? Eventually you wind up at the same point - boiling water. Other factors influence this, radiator cap pressure rating, coolant velocity through the radiator, heat exchange characteristics of the radiator core, air flow through the core, fin pitch, even the ratio of coolant to water in the system. Engine/head water jacket design also has an influence (think Ford flathead V8, one of the greatest contraptions for boiling water known to man).