I guess I look at it from a pessimistic view. What happens when you turn this claim in let insurance pay then 6 months down the road have a decent sized claim that isn't possible to pay out of pocket? Then you have two at fault accidents on your record and are being thrown in to the substandard market. I've had clients that have had this happen and they come in and ask if they can pay back their initial small claim - at that point it's too late.
If the insurance company didn't know about it already and everything is a wash (which is basically is in this case), I'd agree. I've found out the hard way though, that even though accidents without any payout are rarely rated, the technical language is based on the total loss, nothing to do with the payout amount (over state based minimum claim for rating). In most cases, without a claim being filed, the insurance company isn't aware of anything.
In this case, I believe the insurance company already knows. The rental company has probably already filed a claim with them, with the amount of the claim.
Its a bad case of timing and circumstance. The good news is though, without a second event on the record, its slightly cheaper to file the claim and make 'payments', then it is to pay out of pocket. If it wasn't for the credit card coverage to pay the deductible, I would also advise to pay out of pocket and take the chance. Since the deductible is covered, its really a no loss situation to go through the claim process.
Dan