Hi Howego,
Yes there is a significant difference between them. The Ultimate Dreams is a latex/polyfoam hybrid with a 3" latex comfort layer, 1.5" of polyfoam in the quilting, and a polyfoam base layer. The SleepEz 10000 is an all latex mattress with three 3" layers of latex and a wool quilted cover. You can read about some of the differences between a latex/polyfoam hybrid and an all latex mattress in post #2 here.
The Ultimate Dreams is one of the Dreamfoam mattresses that can be customized before a purchase (you can choose the firmness of the comfort layer) but not afterwards while with the SleepEz 10000 all the layers can be customized both before and after a purchase either by re-arranging them or exchanging a layer.
Both Dreamfoam and SleepEz are members of this site which means I consider both of them to be great choices and they both compete well with the best in the industry. Both would make great choices in their budget range and which one would be the final choice that was best for you would depend on the criteria of your personal value equation that were most important to you.
Phoenix