I used to use the Virbac c.e.t. paste. But, with sorbitol as the first ingredient I decided the risks were higher than the benefits. Petrodex, while I have never used it, is made by Sentry, and I wouldn't trust a single product they make for use in my cats.
My cats did tolerate having the c.e.t. rubbed on their teeth and gums, after some training. I never used a brush, just rubbed it on with my finger. It's the enzymatic properties that clean the teeth, not abrasive action.
I don't recommend either one above the other. I have used the c.e.t. and two of my cats had diarrhea that I associated with the sorbitol. I don't think cats should have sorbitol. As for the petrodex, I don't trust any Sentry product. (they don't even list the ingredients, on their website)
Dental health in cats is largely genetic, but you can help by feeding a good low carb canned or raw diet. I actually feed my cats a partial raw diet, and feed meat chunks (balanced with calcium and organ meat), especially chicken gizzards, to help keep their teeth and gums healthy.
Don't waste your money. To be any benefit at all, the paste needs to be an enzymatic paste. Enzymatic means "breaks down bacteria". the petco brand (after checking it out on the site) does not mention enzymatic.
Others may add their own opinions in time, but my opinion remains that the pastes that do claim enzymatic action have too many undesirable ingredients, and the rest are useless.
It's good that you care about your cat's dental health, but the best way, in my opinion, to ensure that your cat's teeth and gums remain healthy is to feed a species appropriate diet such as a grain free, fruit and veggie free low carb canned diet, or a raw diet, or a combination of the two, and take your cat for regular check ups.
I am not a vet, but that is the conclusion I have come to over my years of trials and research.
You know I just looked up the ingredients of different toothpastes and it seems that all of them have some ingredients that is toxic or not good for cats,like sodium benzoate, potassium sorbate,xanthan gum, sorbitol, tee tree oil etc. So why risk my cats health,your right buying toothpaste is a waste of money. My cats actually let me brush their teeth,they are really tolarent. so I was thinking of coutinuing what I have always done, simply wet the brushbrissle with water and brush their teeth!