The "better" argument often comes down to control. Having a local copy of the 3.0.3 update in NSP format ensures that even if the eShop eventually goes offline (years down the line), you can still restore your game to its most stable version. Does it actually make the game "Better"?
By keeping your game updated, you ensure you are taking advantage of all the stability and polish improvements Nintendo has added to make the game better long after the last DLC pack was released. If you are interested, I can: mariokart8deluxeupdate303nsprar better