How Does Power Affect Soldering Irons?
When talking about the wattage of a soldering iron and whether it is enough or not, one really needs to vary from unregulated and regulated tools.
Unregulated soldering irons usually have a fixed wattage that is selected to fit the given size of the tool tip. For electrical and electronics works and small to medium sized tools (usually less than about 2 mm width) 30W should be sufficient. Issues arise when soldering large or highly thermal conductive components due to decreasing temperature of the tool tip.
As to regulated soldering irons, high power ratings mean in that case the ability of the tool to reach the desired temperature fast (e.g. come from stand-by temperature or during soldering of components) as well as the ability to solder components with a large thermal mass (e.g. ground planes or heat sinks) while maintaining the pre-set temperature.