Staying with the same dive op for the week will not only be more convenient, but switching ops during the week would likely up the chances of repeating a dive site.
With the dive op I've used, I've witnessed the DMs being cognizant of where the divers have been the prior days. They always ask where we want to go and divers will usually speak up about where they've been during their trip. I've been asked if I mind going somewhere I've already been if someone wants to go there. It never bothers me to repeat a site, but I've seen others say, "We were there a couple days ago.", and then somewhere else is chosen.
If you're with the same dive op for the whole trip, it wouldn't be unusual for them to know where you've been and for them to keep that in mind.
Also, most of the ops want to see you dive a couple tanks to assess your diving. If you switch ops every couple days, you'll be new to the op and in some respect, kind of starting over.