''Collate results'' would be the ''Best Practice'' option to select, because once the test results have been collated, all the LG's will be released from the timeslot and an available resource for another test.
If ''Do not collate results'' is selected, this will leave all the result files on the LG's, and may cause disk space issues over time.
If ''Collate and analyze results'' is selected, this will hold all machines (Controller, and all LG's) used in the test till after the results are analyzed. For large test, this could take some time and your Host Resources will not be available until the results have been analyzed.