Nondeductible contributions in your traditional IRAs are not a factor because basis in nondeductible traditional IRA contributions does not belong to any particular one of your traditional IRAs.
For tax purposes it does not matter which of these two IRAs receives the rollover. However, for protection against creditors it might be appropriate to roll the funds over to an entirely separate IRA (a "rollover" IRA). It depends on the creditor protection in your particular state afforded to retirement savings.
