I have a 03’ Accord, V6.
I need to replace the battery and would like to know what brand, model is best to use. Thanks.
You will get various recommendations, but my opinion is that batteries are a commodity. The basic design hasn’t changed in 100 years, and most brands are manufactured by 2 or 3 companies. Find the right size and shape, with the right CCA and Amp/hour rating for the lowest price. It’s what the car maker did.
You can check Consumer Reports, or just go to a battery store and buy a good quality battery. Buy on QUALITY, not price. Get the recommended Cold Cranking Amperage (CCA) for your vehicle or slightly higher. There are many quality brand names.
Assuming you are getting the right specifications for the battery for your car, there is not a great deal of difference. In general the more expensive ones will last a little longer but will they cost more. 
I would not worry too much about brand or model. However that is not to say your asking was stupid or you should ignore the information are are getting. I suggest you pay attention and when in doubt by the better battery even if it cost a little more.
Go to WalMart. Their batteries are rated very highly and are relatively inexpensive.
My advice is to buy the biggest, most powerful (highest CCA) battery you can that will fit in your car.
Or, get the exact same one used originally by Honda. It lasted for 4 years, so it must be an okay product.
I second the Consumer Reports advice. They do a reasonable battery test. If you live in a very hot place get a battery specific to your climate. If you live in cold place, do similarly. The former have relatively fewer CCA, but they are constructed to dissipate heat faster while charging and are resistant to other heat-related problems. The latter just pack in thinner plates.
I disagree that with the implication that batteries have not changed much in 100 years. The chemistry has been tweaked and the construction has been improved. Chemical improvements can prevent plate sulfation and polarization, and better construction reduces warped plates.
This is not to say that improvements in the auto electrical system have not contributed to longer battery life. Better charging control and batter-saver circuits are both a real boon.
agree, as a minimum get the same CCA as the original or higher. I have had good luck with Advance Auto but as noted, there are only a few actual manufacturers in the country, specs may vary but basically the same
Go with the cheapest, I don’t know why, but I’ve had much better luck with them than the top of the line batteries. Unfortunately, you will find that Honda uses odd sized batteries for some reason and you may not have much choice. Try to get one with removable caps so you can check the electrolyte level and add distilled water as needed.
I have had good luck at Wal-Mart and Auto Zone.
Yes, there have been all sorts of incremental improvements in lead-acid batteries, but it’s still 100+ year old technology and the improvements are not top secret advances. It’s just better materials and better manufacturing techniques that everybody in the business knows about.
Like I said, they are commodities. Buy a really expensive name brand and it will last 5 or 6 years. Buy a cheapo brand with the same specs and it will last 5 or 6 years. I know others won’t agree, that’s just my take on it. They are just batteries not swiss watches.
If you are planning on keeping the car for a while get one that has a good warrante, 60 months or longer. If you live where is gets cold get a higher CCA rating that speced as an insurance policy for starting on cold days. Also, check the date code stamped or labled on the side. You want to pick out the freshest one on the shelf if you can.
The shopping clubs like Sams and Costco have very good pricing but limited selection.