Chasing and setting are different crafts with the same scoreboard

The chase removes the guesswork

A side batting second knows exactly what it needs, which converts a strategic question about how many runs are enough into an arithmetic one. That certainty is an advantage, because every decision can be measured against a fixed requirement rather than against an estimate of a good total. It also removes the temptation to accelerate unnecessarily, since a chase that is comfortably ahead of the rate has no reason to take extra risk.

The disadvantage is that the arithmetic is visible to everyone including the batters, and a rising required rate creates a pressure that estimation does not. Sides that chase well tend to break the target into phases rather than treating it as one number, which keeps the requirement in a manageable range.

Setting a total is a judgement about the surface

A side batting first has to decide what a defendable score is on a pitch it has only just begun to understand, which is genuinely difficult. The estimate comes from how the ball is behaving early, how much the surface is holding, and how the boundaries are distributed around the ground. A misjudgement in either direction is expensive, since a side that sets its sights too low is overtaken and one that aims too high loses wickets reaching.

The estimate also has to be revised continuously, because the pitch changes and a total that looked adequate at the halfway stage may not be. This is why batting first is often described as harder in the shortest format, even though the pitch is usually at its best.

Where the pressure arrives

In a chase the pressure builds gradually and then concentrates, because the required rate rises with every dot ball and becomes visible in a single number. In an innings batting first the pressure is diffuse, since there is no external measure and the batters are competing against their own estimate. That difference changes shot selection, as a chasing batter can calculate exactly how much risk is necessary and a setting batter has to guess.

It also changes how a partnership behaves after a wicket, because the chasing pair knows precisely how much time it has to rebuild. Neither situation is straightforwardly easier, and players tend to have a genuine preference based on how they respond to explicit requirements.

The bowling side's mirror

Defending a total is a containment problem with a hard boundary, and every over can be evaluated against a simple calculation of what remains. Bowling first is a wicket-taking problem, because a captain cannot know what total will be enough and can only try to limit the opposition's ceiling. That is why fields tend to be more attacking in the first innings and more calculated in the second, even against the same batters.

A captain defending a target will often accept singles freely late on, since the requirement makes them insufficient and the boundary is the only threat. The same captain bowling first would not make that trade, because there is no number against which the singles can be judged harmless.

Dew, conditions and the limits of planning

Conditions change between innings in ways that neither side controls, and evening moisture on the outfield can make the ball difficult to grip. A bowling side that expected to defend with spin may find the ball skidding on and the variations impossible to execute reliably. Captains factor this into the decision at the toss, but the factoring is a probability rather than a certainty and the conditions frequently disappoint it.

The craft response is to have a plan that does not depend entirely on the conditions holding, which usually means bowlers with more than one method. Sides that plan around a single expected condition are the ones whose strategy collapses when the evening behaves differently from the forecast.