Thanks for the question! These two tapes have a few differences:
1. 4926 is part of the larger 4941-family of VHB tapes. The 4941-family of tapes has excellent adhesion to a broad range of high and medium surface energy substrates, and a conformable adhesive foam core that provides good contact even with mismatched substrates. The combination of foam strength and conformability typically make this family of tapes the best all-around option.
RP62 is part of the RP-family of tapes. The RP-family is a good option for general-purpose applications.
2. Within the 4941-family and RP-family of tapes, there are different options for tape thickness. 4926 is the 0.015″ thick offering within the 4941-family, and RP62 is the 0.062″ thick offering within the RP-family. A thicker tape can provide better contact between two substrates, and allows more shear movement between substrates.