One of the things I have realized with researching a catted DP is going to be placement is critical. Seems that the closer is it to OE (close to turbo) the fewer the problems such as CELs, use of spacers, smell, emissions etc. The IE uses a "race" style catalyst that has fewer cells to help with flow. It being close-coupled to the turbo does allow for a faster light-off, thus reducing smell and emissions, and also allows for proper post cat placement of the O2 sensor without need for a spacer to "fool" the ECU. Some manufacturers are using a larger catalyst that is located downstream to make up for the loss of catalyzing efficiency. This seems to be done more from a cost and ease of manufacture standpoint than anything else. Because of the more downstream cat location, some pop CELs, some smell more, some won't pass emissions tests, or other issues. Seems to be more difficult to package a catalyst in the OE location, but overall, you should get better results regardless of the cat size or type if they use something decent. Precious metal matrix catalysts are very similar in their performance if placed correctly. IE uses this type of catalyst placement and I would suspect few will have any issues with it.