Is there a catch?
 

I'm renting for 6 days out of ANC and I tried these two methods. I am <25...

via Hertz US,
Gold Family CDP + free day promo code
I get about $440 incl taxes and fees

via Priceline.com.sg,
I get about $480 incl taxes and fees and LDW too!
I put in PC 144314 which I hope will still work to waive the <25 fee, but right now I don't know for sure

In theory I am covered by my VISA's auto rental CDW, but if anything does happen (tree branches, rocks hitting windscreen, whatever) I am imagining that it'll be much more hassle to go thru VISA then to go thru Hertz's own LDW?

Is there a catch somewhere, since I'm only paying $40 more for Hertz's LDW for the entire rental, while they normally offer it at ~$30/day?

There seem to be a couple of catches. First, the LDW bought through Priceline is not Hertz's, it is a separate product offered and run by Priceline, as far as Hertz is concerned, you haven't purchased their LDW and if the car is damaged they will pursue you for the charges and you will have to file a claim with Priceline (or whatever subcontractor manages the product) for reimbursement. Second, you may have trouble having the underage PC apply to a rental paid through Priceline, obviously PCs that discount the rate aren't applicable, but one for a supplemental charge may work though it's not a guarantee.

hm but when i went thru priceline it basically directed me thru Hertz Singapore, and I received the email from Hertz SG that stated as such:

The total rate for your SPECIFIC RATE was calculated based on the following:

Discounts
CDP: HUTCHISON PRICELINE TRAVEL LTD
PC: 144314

Base Amount:
1 week at 479.20 USD
Unlimited Free Miles Included

INCLUSIVE ITEMS:
Airport concession fee recovery
Loss Damage Waiver
Taxes
Liability Insurance Supplement
Vehicle Licensing Cost Recovery
Customer Facility and Facility Maintenance Charge
ENERGY SURCHARGE


This should mean that its Hertz's LDW, no?

I would make sure that there is the underage supplement there in the rental through Priceline, or it's waived. It's not listed in the quote you have, and I'm not even sure priceline asks for your age when you are reserving a car (though may use your profile information)