I used to do kitchen installs for a major company. Tile/flooring under the cabinets was our preference. When/if the cabinets need replaced or upgrading in the future but the tile is still wanted, you are stuck with the footprint of the old kitchen. Also, the standard counter height of 36” is based off of a 34.5” base cabinet, so whatever your flooring height is can throw that off if added later, unless you shim that extra amount in the cabinet install.