Always check all copies of records which have been filmed multiple times.

This example from Union Co SC records(Will of James Prince--recorded 28th of September 1789) shows the value of checking BOTH copies of microfilmed records. 

Union District, South Carolina, miscellaneous records, v. 1-2, 1785-1800
Format: Manuscript/Manuscript on Film
Publication: Columbia, South Carolina : South Carolina Department of Archives and History, 1974
Physical:  1 microfilm reel ; 35 mm.
https://www.familysearch.org/ark:/61903/3:1:3Q9M-C959-696F?i=68&cat=341333

Missing(or covered?)  lower left corner

From 1974 Filming(Image 69 of 256)

Listed under the same main catalog entry and noted as follows

Another filming. Made in 1961 from originals at the Union County Courthouse, Union, South Carolina

https://www.familysearch.org/ark:/61903/3:1:3Q9M-C9P1-L3JT?i=68&cat=341333

.

From 1961 Filming(Image 38 of 174)

The catalog listing makes it appear that this is an earlier listing done by SC Dept. of Archives and History.  Image 4 of 174 makes it clear that it is not a filming by SC Dept. of Archives and History with the following notice:

"This microfilm is not an official publication of the South Carolina Department of Archives and History.  All Queries concerning this film should be addressed to the Genealogical Society of the Church of Jesus Christ of Latter-Day Saints.

50 East North Temple Street,

Salt Lake City, Utah 84150."

So in this case the earlier filming was more legible and contained the missing or covered left lower corner.  Regardless, the answer of which of the film to check when there are multiple filmings of the same records is ALL.