We had a blind taste testing at work to compare Shiraz samples.  The 1st place went to McManis Family Vineyards Petite Sirah (which I've reviewed separately in the past on this blog and scored an 8 out of 10).  Regarding the remaining samples:

Red Diamond, Shiraz, 2002 (Washington) - Came in 2nd, had decent flavor and really gave McManis a run for the money - especially since Red Diamond is cheaper at only around $10 a bottle.

Barefoot, Shiraz (no year)(California) - Came in 3rd.  Despite the lower ranking it was still drinkable and enjoyable and at only 2 for $11 it's a good value.

Bota Box, Shiraz, 2006 (California) - Came in 4th (last) but was still drinkable despite that.  Granted it was thinner and weaker than the rest but it did have decent flavor.  It's around $19 a box but it holds the equivalent of 4 bottles so it's actually the cheapest of all the samples.