The fields will be treated as equivalent in sorts, finds, relationships and calculations.
You can also clean up the capitalization on your entire table to make it consistent very easily by using a calculation with Replace Field Contents just to make it look nicer.
Usually you would only worry about the display of the data which can be controlled by layout-level formatting to 'make it look nicer'. So if you select the field and then Format > Text, you can set it to Title Case or whatever you wish. Although true that case sensitivity won't usually matter in calculations, it does matter in Substitute() and Filter() and it would matter if the field is set as Unicode.
However, when Users enter data, they mix caps all the time and it usually isn't an issue. If you use Replace Field Contents remember two things, 1) it does not produce proper error trap when ran in multi-user so run it when nobody else is in the system and 2) it would only be 'fixed' until another User potentially types into the field.
If it is very important to you that the data be exact then I would rather use auto-enter (with 'do not replace existing value...' unchecked) and apply the 'fix' there with calculation of Proper(). But I wouldn't bother in most cases.
Thank you very much! As usual, the Forum community has been a great help!