R12- Upgrade Vs. Re-implementation

Upgrade Consideration
1) No major process changes
2) No major organizational restructuring
3) COA unchanged
4) Current system is cleaned, reconciled and up-to-date

Re-implement Consideration1) Major business process changes
2) Major organizational restructuring
3) Significant setup changes required (Eg. New COA)
4) Geographic expansion (New country roll-out)
5) Multiple environments to be merged
6) Heavily customized
7) New application to be implemented
8) Historical data can be viewed separately

For more detailed factors/parameters, visit discussion below
http://www.infosysblogs.com/oracle/2009/10/ebs_r12_roadmap_upgrade_vs_rei_1.html