My wife and I are at an impasse; I thought they were two different names for the same wine, but who knows?

Shiraz and Syrah are two different names for the same grape variety.

Winemakers can choose which name to use on the label. You will find French wines labelled as Shiraz now and you will find new world wines labelled as Syrah.

Often the name used is meant to signify the style of the wine - i.e. those using Shiraz suggest their wine is in the big Australian style, and those using Syrah imply theirs is in the French Rhone style, but sometimes it is just marketing. Some wineries in southern France who changed the name on their labels from Syrah to Shiraz found they had much greater success in export markets as more customers were familiar with the Shiraz name.

The person who said that you'd never see a French wine labelled Shiraz has obviously never come across the big selling Fat Bast*rd.

And, although there is a Persian city with the name Shiraz there is no evidence the vines came from there -- in fact there is DNA evidence to the opposite -- see http://www.winelabels.org/artsyr.htm

It is the same thing - the Aussies call it a Shiraz.

The grapes are the same, but the difference is in the style of the wine.

If the wine is labelled a Syrah, it probably follows more of an "old world" model, based on the wines from the northern Rhone Valley of France which are 100% Syrah. The aromas and flavours of a Syrah may feature more subtle fruit than a Shiraz, and there is usually a prominent black pepper aroma. I often find herb and game notes as well as licorice in Rhone Syrahs.

Shiraz is made from the same grape, genetically. However, the grapes are riper, and the wine maker usually uses more extraction resulting in a more full bodied, jammy, fruit forward and high alcohol wine. This is the Aussie style. It's rare to find the trademark pepper notes of Syrah in a Shiraz. Also, the prevailing tendency is to use new American oak for aging, which will lend mocha and vanilla notes to the wine's flavour profile.

Hope that helps!

Cheers!