LogPlot's sole purpose is creating logs: It generates individual well/boring logs with almost unlimited flexibility in log layout, with detailed headers, footers, and any combination of data columns. You can create the graphic log at any vertical scale and print to single-sheet or continuous printers. If you need detailed individual logs, LogPlot is the way to go.
RockWorks creates more simplified logs, designed for display in cross sections and fence diagrams, and as a launching point for project-wide data interpolation and display. Logs are just a small part of what RockWorks does.
RockWorks and LogPlot can share data, so they work nicely together, and can be purchased separately or as a bundle with a discount.