...So, I now try and buy everything on B&H when possible, using the Pay Boo card, which as everyone now knows, credits your sales tax back at purchase...I, also shop Adorama a lot but mostly for specials, as long as the combined price + tax is less than what I can buy it for at B&H or it is an item unavailable elsewhere.
For a direct comparison: B&H credits the sales tax back on purchases; Adorama offers a 5% rebate on purchases plus a rewards point system that is an additional 1% credit. At times, on specific items, Adorama ups the reward points.
Both use store cards issued by Synchrony Bank. Both offer an option to make payments interest free for a specified time period, usually six months, instead of the rebates. Both charge the same interest rate if you don't pay it off immediately, which is somewhere north of 20% interest, so you don't want to use the cards unless you can pay it off immediately or unless you need the interest-free period to pay it off (but you lose the savings). If you do need the interest free financing, I recommend Best Buy, which generally offers longer terms -- sometimes up to two years on major purchases.
So, if your state sales tax is less than 6%, you save money with Adorama. Over 6% you save money with B&H. But, to keep it in perspective, you might want to do the math. Say your state charges 7.5% sales tax, a 1.5% difference between B&H and Adorama. If the R3 is $6,000 that 1.5% difference between Adorama and B&H would amount to a grand total of $90. Not a huge difference on a $6,000 purchase.
One note of caution. If you are considering a purchase, it's best to apply for the cards in advance. With Adorama I had no problem getting immediate credit approval and using the card, with B&H I had to wait for the card to come in the mail because I could not check out without having the CVC which they would not provide over the phone.