This calls for speculation. The Pixma Pro-1 is definitely capable of dazzling prints (I'm an Epson kind of guy, have been for many years, and I'm impressed enough to consider it), so it's likely down to the printer/paper profile being used (assuming that particular printer doesn't have a problem).
You should notice a distinct difference between the Pro-100 and the other two models It uses dye-based inks (where the other two used pigment-based inks), and while that's great for some things (landscapes, still life/product shots) it can be a little garish at times (with skin tones being over-saturated, for instance, giving people a kind of glow-in-the-dark look). The differences bewteen the -10 and -1 should be less easy to spot at a glance, with the -1 capable of smoother tonal transitions, and the -10 being somewhat darker in the deep shadows (because it lack the dark grey ink and needs to use black). That, however, depends on the print job being set up properly.
The two newer printers (the -100 and the -10) manage their paper profiles differently from the Pro-1 by default, the expectation being that the user may not be printing from an application that makes colour management tasks easy (or possible at all in any real sense) or may not be sophisticated enough to understand colour management. You need to enable "pro mode" to take back control from the printer. To get the same behaviour from the Pro-1, you need a firmware upgrade (although I'd expect that newer shipping models would come with the upgrade already installed). Profiles make a huge difference in printing; the wrong profile for the paper (or the right profile applied twice) will result in, to put it gently, a less-than-optimal print, with various inks applied either too heavily or too lightly.
In some ways, this is a whole lot easier with "stupid" printers having only a handful of "close enough", manufacturer-specific paper choices available. You know that you're going to have to override the printer with custom profiles (created with something like the SpyderPRINT or ColorMunki Photo) if you want anything better than meh, even on the printer-brand papers. Turning off colour management at the printer and using known-good paper profiles from the printing application (eg, Photoshop) is just something one does. The new Canons are designed to accept "straight" data and apply good profiles locally in their built-in RIP (like the high-end, self-calibrating wide-carriage Epsons) by default. The trick here is knowing what settings to use when.
