GradPLUS is a fixed rate loan, if the other is not, I would go with the GradPLUS, regardless of any incentives.
Copied from the graduateleverage.com site:
"Here are some considerations to weigh when deciding which option is best for you:
When to choose a PLUS. All students receive the same interest rates on PLUS loans. Because of lender incentives, the actual rate usually falls between 7.25 percent and 8.5 percent. In contrast, private loans offer rates that are tied to your credit rating. When deciding between PLUS loans and private loans, be sure to compare the best possible private loan rate against the current PLUS rate. If, after reading the fine print, you determine that the rate for the private loan exceeds the PLUS rate, then you should definitely choose the PLUS loan. If you would like assistance in completing this, contact Graduate Leverage for a personalized analysis.
When not to choose a Private (maybe). If the private loan rate is lower than the PLUS rate, you may want to go with the private loan. We say "may" because PLUS loans are federal loans and therefore can only be acquired by current students. Private loans, on the other hand, can be taken out after graduation via private loan consolidation. Thus, if you've taken a PLUS loan instead of a private loan and interest rates drop significantly after graduation, you still have the option of switching to a private loan through consolidation. If, however, you choose the private loan over the PLUS loan in order to get a marginally better rate, only to discover after graduation that rates have increased significantly, you won't be eligible to switch to a lower-interest PLUS loan. As a result, if the rate you could obtain on both loans was the same (say 7.5%) then the decision depends on what happens to interest rates in the future. If you take a private loan and rates increase, your rate will be above 7.5% and therefore you would be worse off. On the other hand if you took a PLUS loan and interest rates decreased, your loan would still be at 7.5% (while the private loan rate will have dropped) and as a result you would be worse off. The final catch again is that PLUS loans can be converted into private loans but private cannot be converted into PLUS. So if you're still confused here's a rule of thumb for you: if your private loan rate is not more than 0.5% less than the PLUS rate, take a PLUS loan. Again, completing this analysis can be overwhelming and time consuming. Please feel free to contact Graduate Leverage for a PLUS vs. Private loan evaluation at no cost to you."
http://www.graduateleverage.com/fivethings.aspx
