The images are of quite a high resolution — they're even better than what you can get with celestia [0] and the (amazing) best surface and normal maps (by John van Vliet) [1]. Compare [2] and [3].
Celestia still has advantages — nicer zoomed out view (due to lack of "striping"), better navigation, arbitrary point of view, offline access. (Also, the lack of sufficiently detailed planetary maps adapted for Celestia isn't technically a flaw of the program itself.)
[0] https://celestiaproject.net/
[1] http://celestiamotherlode.net/catalog/mars.php