Hi, I am flying the following route (all flights are on one ticket, open jaw):
BOS-YHZ-LHR + CDG-YUL-BOS, booked on Orbitz.

US-Canada leg - AirCanada (operated by JAZZ)
Canada-Europe - Lufthansa (operated by AirCanada)

What program for miles would you suggest to use for this flight to get the best value? I am US-based, and I am nowhere near hitting a loyalty level with one of the programs. Meanwhile I put "one pass" as default, but after doing some research, I think Aeroplan has more value. Any thoughts? Thanks in advance.

Fares:
SKX6NCE
SKWNC95N

You're looking at about 7300 miles roundtrip assuming 500-mile minimums.

If you really are not going to add to that, it's not going to get you very far.

Off the top of my head, that will get you a gift card to one of many retailers with AC's program, or get you very close to a cash+miles one-way within North America with BD's program...

Have you considered adding to these miles with a New Credit Card?

I am new in the US, so getting a new credit card is kinda tough. I have Delta's Amex though, so it will be no use here.

I still sometimes fly around US, making a couple of trips to Europe and Middle East during the year. I would really like to start piling up miles, and I just have to figure out which program has better value: Onepass, Miles&More, or Aeroplan.

What's BD? Sorry, I am new to this.

It's the two-character code for BMI. Their program, Diamond Club, has a lot of good points. (More discussion in the BMI forum on FT.) However, it might not be the best choice for you because Lufthansa, which owns BMI, currently plans to integrate DC into their Miles and More program sometime next year. This is good news/bad news, but for someone in your situation mostly bad news. Most awards require more miles on M&M than they do with DC, and M&M doesn't have the DC option of getting an award ticket for half the usual miles plus a reasonable cash supplement.

S class earns only 50% mileage on Lufthansa flights, but I'm not sure what the rule is for LH flights operated on AC metal -- you may be able to get full miles. I'd check with Aeroplan.

The guiding Star Alliance principle is that mileage earning is based on the operating carrier, no matter whose flight number you book. (This is the opposite of oneWorld practice.) What makes things complicated is "fare bucket mapping:" a flight booked in one class with one carrier may be mapped into a different fare class on the operating carrier. You cannot simply take the fare class you book, look at what that fare class earns on the operating carrier, and assume you'll earn that multiple of your miles flown. That may not be the fare class the operating carrier puts you into.

Also, there's no simple way for people to find out what fare class a given fare class on the selling airline maps into on the operating airline. (You can do it if you have ITA access, but most of us don't.) The major classes - F, Y, B, a few more - are standardized across all *A carriers, but many of the deep-discount economy fare classes are not. Your best bet is to call and ask.

And the Y code isn't even standard though out *A. For instance, Y on SK is their economy extra product, and when airlines rebook economy tickets they are suppose to use M class instead of Y for the SK parts. Fairly confusing. A few years ago a UA rebooking booked me on Y all the way, and a SK representative put me back down in economy in such a way I try not to fly them anymore.