One positive factor would be that in-wall you have essentially an infinite baffle so the speaker always radiates into 2 pi space so no baffle step compensation (up to a 6 dB impact on sensitivity) is necessary. You would have the ability to conceal (if SAF is a factor and I assume that it is) and present a clean, uncluttered environment within your room--no speaker boxes in the mix. Not everyone has a room large enough to house a set of line arrays and in-wall you can alleviate that worry.

The negative side includes that absence of flexibility to move the speaker enclosures around for best sound within the room. Plus you effectively will make your room layout set as any future movement of furniture around the room may not yield acceptable sound.

Jim