Old Orchard or Shediac?
-At about half the distance, if you are driving, Old Orchard wins.
-Flying? Porter flies direct from Ottawa using a plane that leaves Toronto Island airport. Air Canada does Montreal-Moncton. Westjet and Air Canada do Pearson-Moncton. And get this, Westjet, in the Summer, does Hamilton-Moncton! I suppose you could fly to Boston if going to Old Orchard. You can actually get to Old Orchard from Boston by train (if you want to avoid a rental). Boston's airport is 150 km from Old Orchard Beach. Moncton's airport is 23 km from Parlee Beach. Conclusion, if flying, Shediac wins.
-Old Orchard has one on the beach. Shediac? Well, nearby Moncton has a small indoor one.
-If taxes are your obsession, you can save big by going to Old Orchard (Maine: 5% (prepared food 7%), New Brunswick: 13%), as long as you don't eat or spend the night in New Hampshire (9%) (but it is OK to shop there: 0%). Keep in mind New Englanders are big spenders when it comes to other taxes such as property, estate and corporate taxes. All those can find their way into your bill, as they have an impact on the relative costs of doing business. Also, health insurance costs are significantly higher in the US for low paid employees than they are in Canada.
-Gas tax is also significantly cheaper in the USA. So much so that many in New Brunswick's border communities cross over for the sole purpose of tanking-up (you could as well when you pass Edmundston, Saint Leonard and Grand Falls, or get to Shediac via the Maine route).
Unless you have a yacht you can sell and a house that you can mortgage, you need health insurance when travelling to the USA. You can do without in New Brunswick, particularly if you live in Ontario. Prudent Quebeckers should get insurance, as New Brunswick charges more than what Quebec reimburses. Both nearby Moncton (Shediac) and Portland (Old Orchard) have adequate hospitals and other emergency care options. Many employers provide travel health care insurance, so that could be a tie for you. $30 extra per person if your employer is stingy and you choose Old Orchard.
-No tolls in New Brunswick. Only tolls in Quebec are across the new bridge from Laval to East-Montreal ($5 per crossing when you don't have a transponder). I95 is a toll highway in Southern Maine, so expect to pay a few bucks each way when going to Old Orchard. If you decided Shediac isn't far enough and want to venture onto Prince Edward Island, 85 km away, then expect to pay $45 per car (you pay on the way back).
Both Shediac's Parlee and Old Orchard's beach are nice. Both also offer nice day-trip beaches 90km away if you need a change of beach venues (Hampton and Kouchibougouac). However, in the Summer the water will undeniably be warmer in Shediac. On the plus side, the water is usually too cold for even the jelly fish in Maine (but they have sharks). The waves are also significantly higher in Maine, as Shediac's beach is sheltered by Prince Edward Island, across the Northumberland Straight. Despite the cooler water, the air will probably be warmer at Old Orchard, as it is significantly further south.
The local season starts in August in Shediac. But further north they start in June. Fall is peak lobster fishing time in Maine, although they can legally fish year round. Neither location is know for their cuisine, and you will have to hunt unless you like your clams deep fried.
Beaches suck when it rains. Both Southern Maine and Southern New Brunswick have many sites worthy of a visit, but if it is raining, you probably won't be in the mood. Both Moncton and Portland have big malls within 30km, and both are on the beach side of town. Moncton has a zoo and a museum and a small indoor amusement park. Portland has many small museums. The city itself is fairly old and worthy of of a visit. Cities aren't why you are going to the ocean, so lets call it a tie.
Places to stay
Old Orchard definitely has more accommodation options, but if they are all booked up by beach crazed Quebec construction workers (they have a mandatory vacation during the last two weeks of July, in 2012, from July 22 to August 4) it is a moot point. Shediac only has one small hotel, and nearby motels are few and far between. But there are camping options, and Moncton is only 30km away.
Getting there is half the fun, right?
Going to Old Orchard or Shediac, you will be crossing Appalachian forests. Scenic? Sure. But it gets old real quick. Going to Shediac, you have the option of stopping in Old Quebec and Old Montreal. Going to Boston on your way to or from Old Orchard is an almost 300 km detour. Both Mount Careleton in New Brunswick, 800m, and Mount Washington in New Hampshire, 1800m, are kind of on the way to the beach, and can present interesting diversions for mountainly challenged Ontario residents. Mount Carleton offers a hard way and an easy way to walk up. Mount Washington offers a road and a train! Both mountains are the highest peeks in their respective regions (Atlantic Canada and New England). Going to Shediac, you can return or go via Maine. But don't do it for the change of scenery unless you plan on visiting the towns, as it is the same forest and the same mountain range as in New Brunswick.
You'd never know from the signs, but Shediac is a French speaking community. Inversely, Old Orchard is very much an English speaking community, despite all the French signs aimed at vacationing Quebeckers.
Unfortunately, thanks to Obama, who is from Hawaii, Canadians need a passport to walk, bike, drive, canoe or fly into the USA. Thanks to Canada's federal government, passports are expensive as the passport fee is used to finance European embassies. Quebec is still Canadian, so you can get to New Brunswick without a passport.
If you can't decide between Old Orchard and Shediac, flip a coin! There will be an other Summer next year...