SWOT and PESTEL analysis which is the best business tool?

SWOT Analysis

This is often used in the initial stages. SWOT analysis helps to focus on what the external and internal factors are: Strength,Weakness,opportunities,threats.

whereas 

PEST Analysis

This is a framework you can use to analyze the external environmental analysis. The process entails learning about various external factors which affect the organization: Political,Social,economic,technological etc.

both are emerging technologies in their area :-)