As an ECW in M9, the ECW of the orthophotos was about 268 MB. In M8, as a map containing the merged orthophoto plus one vector layer of the area boundary, the resulting image file was 1.2 GB.
Ah, but exporting that image to ECW format, which is a compressed format, would greatly reduce its size.
I agree with Tim that I miss the ubiquity and simplicity of Make Image. I expect we'll have that soon in 9. But I respectfully disagree it's the best approach here.
As I understand it, the objective is to provide high resolution photo data with a vector overlay to a client, but to do that using small files and a simple viewer. ECW is a compromise for that because to get small files in ECW you throw away data. It doesn't seem you are throwing away data because ECW is clever about visually compressing data into what is left, so what you see seems to be pretty good. But you are definitely throwing away data. I don't know what viewer you are using with ECW, either, but if it is simple enough for the client, OK.
PDF is universally acknowledged as acceptably easy for non-technical clients. One approach is to use a different PDF printer to output your layout in 9 as a PDF to get a more compact PDF. PDF printer software varies very widely in capabilities, quality, and size of output. See the File - Print topic for some commentary on that.
FWIW, reconsider using Viewer. If the user installs a regular installation, all he has to do is double-click a .map file and the thing opens. He then double-clicks the image and it opens. Navigating in images is exceptionally easy in Manifold - way easier than things like Photoshop. You can name it "Double click on me" to make it very easy. You can then give your user a full resolution image with no ECW degradation, overlaid with super detailed vectors, and it will all run very, very fast.
With just the slightest bit of coaching your users will be able to get way more out of projects than just looking at a static ECW. Something to consider.