Both words are adjectives but they have different meanings.
- Despite creating high levels of public debt, the government’s new ________________ policy was welcomed by businesses.
- Use of robots in production is very ______________, but it raises questions about unemployment and ethics.
Economic is a more general term and it is much more commonly used in the social sciences than economical. One of the definitions of economic (requiring fewer resources or costing less money; see 2.1 below) is very close to economical (giving good value or return in relation to the money, time or effort expended). It is more usual to use economical in these cases.
Another explanation: Cambridge Online Dictionary Grammar
1 relating to economics or the economy
The correct answer is thus
1. Despite creating high levels of public debt, the government’s new economic policy was welcomed by businesses.
‘It can be argued that predatory lending by banks contributed to the economic crisis.’
‘Economic factors were important, but social factors had a decisive impact in this case.’
‘Moreover, the political situation, worsened by great economic hardship, remained extremely tense.’
- (of a subject) considered in relation to trade, industry, and the creation of wealth
‘Economics and lessons from economic history suggest that this may well be the case.’
2 justified in terms of profitability
‘Many organizations must become larger if they are to remain economic.’
‘The advent of cheap online communication made international collaboration economic.’
2.1 Requiring fewer resources or costing less money.
‘Solar power may provide a more economic solution.’
‘Many car parks are disappearing because high land prices make building flats more economic.’
1 Giving good value or return in relation to the money, time or effort expended.
The correct answer is thus
2. Use of robots in production is very economical, but it raises questions about unemployment and ethics.
‘Small economical cars are better for the environment than large vehicles which consume more petrol.’
‘The parliament voted for the second plan, as it appeared to be more economical way to achieve almost identical results.’
1.1 (of a person or lifestyle) careful not to waste money or resources
‘The study showed that people who survived the war tended to be very economical as they had learned to be careful with resources.’
‘The new government was very economical and managed to decrease the country’s debt without cutting social programmes.’
1.2 Using no more of something than is necessary
‘The author is very economical with his words, his writing style being very clear and concise.’
‘The company redesigned the car to be more economical with fuel.’
Source: Oxford Online Dictionaries