SD vs HD channels difference?

Is there still a difference between the regular channel numbers (ex. 03, 10, 38) and the 1000 series channels (ex. 1003, 1010, 1038)?  I know that the regular channels used to be sd and the 1000 channels were hd...  but I don't see any difference between them anymore.  FYI...  I live in Pensacola, FL.