An experiment is a systematic way of proving or disproving a hypothesis and used to determine a cause and effect relationship between the subject and its environment. Key differences between experimental research and field study are:

Setting

Experimental research is done in a closed setting or in a highly controlled environment. This lets researchers conduct full replication of the experiment in other laboratories.
Field experiment, on the other hand, takes place in the “real” world (natural settings).

Validity

Laboratory experiments provide the ability to control the environment and confounding variables resulting in good internal validity. Due to the artificial nature of laboratory experiments the results may not be a true reflection of the wider population, i.e., external validity is lower.
Field experiments take place in the participant’s natural environment and consequently are easier to generalise (higher external validity). However, this comes at the cost of internal validity as less control may lead to confounding variables impacting the dependent variable.

Reliability

By standardising experimental procedures the results of experimental research are more likely to be reliable. Random allocation of participants involves randomly assigning the sample to either to a controlled or experimental group, allowing for a direct comparison of conditions. This can reduce the impact of individual differences and also make it easier to investigate whether the IV directly impacts the DV.

Procedure

Experimental research involves random allocation of homogeneous sample to a controlled or experimental group. The experimental group is then subject to variation in independent variable, and the effects are observed.
Field experiments do not provide this opportunity. Similar groups are taken and one set is exposed to intervention. The effect on dependent variable is then observed for both.

Variables

Experimental research: controlling independent variables results in a precise measurement of behaviours and identical conditions for participants.
Field experiments can experience inconsistencies with the control group and often have many confounding variables to eliminate.

Knowledge of experiment

Experimental research: subjects are typically aware of the experiment, even if details are not available to them. The control condition consists of a placebo, which may affect the results.
In field experiment, it is possible to conduct a blind study - subjects aren’t aware they are being scrutinized.

Uses

Social psychologists prefer conducting tests in the field to study subjects’ relationships with their natural surroundings.
Experiments in neuro-psychological studies, on the other hand, are better conducted in a laboratory, where a lesser number of set variables are needed to yield a credible result.

Ethical viewpoint

Laboratory experiments are more ethical in comparison to field experiments. For example, a study conducted by Loftus and Palmer (1974) showed participants a film of a car accident to investigate the impact of eyewitness testimony.  Participants were not viewing the footage first hand and therefore would find the study less distressing, consequently making the research more ethical.

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There are various differences between field and experimental research and the researcher should choose based on what suits the situation best.

Sources:
https://carlymorris.wordpress.com/2012/02/05/laboratory-experiments-vs-field-experiments/
http://www.ehow.com/info_12089230_difference-between-lab-field-experiments.html