I didn't think there would be much debate here but I guess we're not all of like mind on this debate.
Having played all of the main attractions and most of the secondary attractions in both places, I don't think it even comes close. Golf on eastern Long Island is untouchable in the U.S. I'll take SHGC and NGLA any day over CPC and Pebble, though I like Cypress most of the lot, Pebble has a lot more hat than it has cattle in the golf course department.
Pasatiempo can hardly be considered Monterrey, but since my two trips there originated in Pebble Beach, I am willing to include it. As much as I love Pasatiempo (it's in my all time top 20), Maidstone is just as special after even adjusting for the surroundings.
Okay, at this point, you could make a good argument that it's a toss up. Now consider:
Hamptons Monterrey
Friars Head Spyglass Hill
Sebonack Monterrey Peninsula CC
Southampton GC Poppy Hills (I haven't seen the renovation)
Atlantic (if you like this type of course) Links at Spanish Bay
Gardiner's Bay (gem) Pacific Grove
Westhampton Tehama?
Montauk Downs
Addition: East Hampton GC
and since we included Pasatiempo
St. George's G&CC (45mins from Southampton)
In my mind, it's not a fair competition. At the top, it's somewhat close, but the depth of the offerings around the Hamptons does not merit comparison. I have eastern L.I. winning in both categories.
Disclaimer: Apart from the golf, I don't much care for the Hamptons.