Agreed, I think Saudi Arabia definitely has a well equipped, diversified arsenal and military personnel. And I've read news reports about them increasing their spending on military arms, buying the latest equipment and developing their capabilities, so they definitely seem to be miles better than the "trained" Iraqi forces. They also are among the biggest spenders for their military budget, with $67 billion in 2013 (9.3% of their GDP)(Stockholm International Peace Research Institute Yearbook 2013), with Iran only spending $17.7 billion in the same year (according to International Institute for Strategic Studies).
However Iran are no strangers to developing military capabilities either, aside from their ever so controversial nuclear program, they are in the top 10 in the world in terms of active military personnel, and a lot more than Saudi Arabia, from what I've been able to tell.
It would definitely be a large scale war, and one that I would not want to see.