Pair 335:
Found four here and moved on. Caught the extra Omanyte last, oddly. Stared at the one that stayed a bit without noticing the other one (for a little while, anyways).
Pair 336:
Spotted the bag color change quickly. Helped to have the other colors next to it, most likely.
Ferreted out five differences before switching back to the other image (and back again). Ended on Eevee's hat. Tends to disregard those thinner lines more, due to slight image quality changes messing with those more. Did not have to look super closely to realize it was different, though. Stands out well enough.
Cannot believe those light blue squares in the tiles were not added by you. Looks so off. May look stranger due to covering up most of the other tiles with that pattern.