A couple of observations from experimenting. First, Backup- appears to require a higher permission set then Export-. 2, export produces an .xml file were backup produces the typical "DHCPcfg" type file.
Based on what I was reading in the online help files for both cmdlets, it appears they both achieve the same result. A full backup of the DHCP servers scopes including lease and reservation information. Am I missing something? Does anyone else have any experience in this area? Thanks for any thoughts, tips, or guidance!