Tecplot RS will let you load up to 50 different grid files at once, subject to available memory, and you can quickly switch between them or plot them side-by-side for comparison purposes.
To load multiple files, use the same method as to load one file – choose “Load Grid Data” from the Project menu and choose the file containing the data you want to display. Each subsequent time you load data, Tecplot RS will ask you how you would like to handle the additional data with the Manage Data dialog.