Can you change your secondary insurance to primary insurance if your coverage is better with the secondary insurance?

In most cases no. You can not chage due to better coverage. 90% of insurance companies, if not more, have what is called a birthday rule. Meaning if you have dependant children on the policy the guardian who was born first (or who is older) is the primary carrier for the dependant children and the younger of the two guardians is the secondary carrier. If you were to have coverage through yourself and a spouse you would be your own primary, as would your spouse be their own primary. If you are the carrier for both insurances then it would all depend on your plan provisions and restrictions, in which case you would have to question each insurance company as to how they would handle determining what insurance is primary and what insurance is secondary.