@jedmo,

Going through the specs, there are two other small differences between the models that you may have missed.  The RE715 uses slightly more power, and the RE705 currently has CE certification. Which may explain the difference in cost, as certifications usually add an additional cost to devices.

The RE715 is our newest RE, and will most likely have a longer life, and may have a few optimizations that the 705 does not have, however as they are both AX3000 and provide the same speeds, and wireless sensitivities(dBm), you would most likely have an identical experience between the two.