Training Plans with Drills vs Just do the time

A simple question, but many answers... Simple plans for time only are good to

A. build the base endurance and B. keep training simple enough that it gets done. 

Pros of doing drills:  improved form, technique, SPEED, strength and balance (thinking of cycling drills to stand on hills or swimming drills to catch water and roll the body with a fist drill or zipper drill).   Another benefit is the mental focus that drills bring -- you get more mindful of what you're doing when you have a certain way to you're supposed to swim, reps/yards to complete, or cadence to keep. 

Cons of doing drills:  it takes more organization, gadgets/tools for the drill can break, metal focus on days when you want to 'zone out',  and you may find yourself wondering "why am I doing it exactly this way?  wasn't my old way good enough and more comfortable"  They're just harder than going for time alone.

However, getting better, faster, or stronger always takes some effort.  I'd suggest a plan with drills for anyone wanting any of those benefits. 

Cheers, -Sunny