While there are advantages to submitting to the same IC, if the science fits elsewhere, pitch it to the IC to which it best aligns.
Typically, a mentored K award is meant to serve as a pathway to an R01. The usual path is that the K grantee submits their first R01 to the same Institute/Center (IC) that funded their K, ideally around year 4 or 5 of the 5-year mentored K grant. One advantage of submitting to the same IC is that you are known there. If you have been successful on the K thus far, and have a good relationship with your K program officer (PO), it can help position you for success on the R01.
For example, you can ask both the K and the R01 PO at your funding IC to advise you on the R01 submission, and the K PO can offer institute-specific advice and discuss your work with the appropriate R01 PO at their IC. In addition, when it comes time to discuss your R01 submission at the second-level review at Council, your K PO can speak up on your behalf.
That said, sometimes it makes sense to submit your R01 to a different IC than the one that funded your K. For example, your research may have taken you in a different direction and now the R01 project fits more logically into the portfolio of a different IC. In addition, you might have intentionally steered your K project toward another IC that you knew would have a better ESI R01 funding line. While it is not typical for a K grantee to submit their R01 to a different IC, I have certainly seen applicants do so successfully. Have an open and honest discussion with the R01 POs at both the IC that funded your K and any other ICs that might be a good fit scientifically. You could also ask your K grant PO for their advice.
