Structural Functionalism is the theory which focuses on society as an entity in which all of the components work together cooperatively and cohesively for the betterment of the overall society. This theory emphasizes the functions within the structure of the main parts of society and the contributions of each for the overall society's survival and growth.
The STRENGTH of this theory is that it emphasizes the necessity of functions within society. All components of

society must have a function in order to survive and its function(s) therefore contributes to the overall society.

Within this perspective, Robert K. Merton showed that there exists two types of functions; Manifest & Latent,

the former being those functions that are obvious and intended while the latter are those functions which are not

as obvious and perhaps not intended. For example, the economy of a society provides its people with a

monetary base and the means to buy and sell goods (manifest function), while it also fosters social inequality as

not all people have the means to attain the same level of income or wealth (latent function). Whether a function is

manifest or latent, positive or negative, each component of society must serve a function or functions in order for

society to survive. Of course, as with all theories, Structural Functionalism has it weaknesses. The main

WEAKNESS or criticism of this perspective is that it is very conservative by nature and in its conservatism, it

seems to justify problematic aspects of society, such as poverty and social inequality, as simply a way of life, thus 
legitimizing the status quo (Ferrante, 1998). This inherent weakness led to the development of a different theory

which focuses on the conflicts arising from society, Conflict Theory.
Conflict Theory's focus moves away from the cohesion emphasis of Structural Functionalism and focuses more on the inevitable conflict within society. Drawing from the works of Marx and Engels and others, this theory shows how conflict is the catalyst of social change and societal growth, rather than cooperation and cohesion.
The STRENGTH of this perspective lies in its more "realistic" approach of recognizing the inevitable conflict

amongst the classes and any other social relation that is based on hierarchal power structures. Inevitably those

in power will exploit those with little or no power, resulting in an unequal set of statuses and roles. Despite the negative realities of power structures, it is this conflict that is seen as a catalyst of growth and eventual social change. By acknowledging their collective powerlessness, under classic Marxist analysis, together the powerless 
will speak out against their oppression and lead to changes in policy .... though Marx's vision of a Utopian

society has never materialized. The main WEAKNESS of this theory is its overemphasis on the tensions and

divisions between the classes and other groups in society (Ferrante, 1998)as well as its tendency to focus on

economic factors as the driving force behind all human motivation.
Symbolic Interactionism is a bit different than the prior two theories, as its emphasis is on small group interactions and individual processing of the meanings of symbols, rather than on the overall social structure of society. As its name implies, Symbolic Inetractionism focuses on the symbols within a society, their meanings, and ensuing interactions bewteen individuals and groups based on the meanings of the symbols as well as the subjective nature of the symbols' meaning. Social reality then is seen as a constant ebb and flow as different meanings are placed on symbols, thus being defined and redefined through human interactions.
The STRENGTH of this perspective lies in the fact that it enables us to understand the meanings of things drawing

from an analysis of actual human interaction. Where Structural Functionalism and Conflict Theory attempt to explain social reality from the macro point of view, Symbolic Interactionsism takes a much more micro

perspective to analyze the definitions within groups and how these definitions vary from group to group and

person to person. Its strength however also leads to its main criticism or WEAKNESS, which is its inability to

give precise guidelines about where one's attention should focus (in other words, from whose perspective to we

begin to analyze a situation?) (Ferrante, 1998) as well as its inherent inability to appropriatley consider social

structural influences.
SOURCE CITED: Ferrante, Joan (1998). Sociology, A Global Perspective, 3rd edition. Belmont CA: Wadsworth Publishing.