Is it better to save AI pages as pdf and then export them as jpg files for input into master indesign document? (Lots of photos, minimal text)
Scott's correct, in that there is no need to convert the .ai files to any other format before placing in InDesign, but I would highly recommend foregoing Illustrator completely and building your image-heavy pages directly in the .indd.
Assembly and simple compositing of the kind you can do in Illustrator are much faster (on the order of two to three times faster) and simpler in Id, especially when you have a lot of cropping to do, you need to fit images within odd-shaped frames, or you find yourself tweaking the position or size of images within their frames. Not only do you get your page layouts done faster, you also eliminate the extra step of placing already-composed pages in InDesign.
I agree with both previous responses and would add that it's always best to decide upon the appropriate application for the type of job you're doing - in this case, that would be Indesign as it is specifically a layout tool. Thus it's best configured to do all the things you want to do to unite the various elements - text and images - into your 250-page publication. While Illustrator has the same elements of this functionality built into it, page layout is not its core purpose - it is better suited to creating vector-based illustrations, logos and graphic elements for use WITHIN layouts. I have a very simple rule for all my work - Photoshop for photos, Illustrator for illustrations, Indesign for layout.
Best of luck with your work :-)
I've just been facing this problem, for placing webpages comps into an Indesign presentation. After multiple tests (JPF high quality, PNG, PDF) playing with settings, matching the target size I need etc, I feel placing the AI file in inDesign then using the option "Object Layer Option" to select the layers you want works the best.
Hope this helps.