This line of thinking is putting the cart before the horse.

Pilot group size is an irrelevant metric between competing airlines, other than the fact that pilots are expensive. In fact, DL would be happier to fly the same volume/revenue as UA with fewer expensive pilots. This might be considered winning.

That said, market share is absolutely a metric in the thinking. Even at the expense of profitability in some places, market share is key. To feed the market requires airplanes, and airplanes need pilots. Soooo... yea, DL might want to indirectly match pilot group size with UA. But the number of pilots come last in the equation, not first.