I wouldn't get hung up on fabricated versus stamped decks as the only factor for the deck.  Also consider gauge of the material, quality of the brackets and wheels, and flow/performance.  Manufacturing advances make it possible to build a heavier stamped deck nowadays, whereas in the past it had to be fabricated.  Stamped tends to have better airflow and less clogging/buildup issues because they can build it with smoother shapes.  Many of the high-end professional zero-turn mowers (of multiple brands) come with a stamped deck nowadays, and same goes for some of the mid-mount-mowers on compact tractors.  Really comes down to what they can manufacture based on the various requirements and specs.  If they can do it with a stamping, that's the best of both worlds.