I prefer a 24" Ricardo Bevery Hills luggage. I've flown with it many times, and it's incredibly sturdy. My cat used her claws on it one time, and I thought it would be ruined; I can't even tell where she did it!
For you however, you'll need at least a 26", but most likely a 29". I don't like to carry a 29" because they get too heavy, but if you want to only use one luggage between the two of you, I'd look at the 29". Also, it's very easy to go over your 50 pound limit by the airlines, so watch what you're packing.
I use to sell luggage, and these are the things I know, and would tell other people. What I'm refering to is the middle of the line luggage, which I feel is perfectly good enough. I doubt I'll ever buy top of the line, because as well made as luggage is today, there's no need to pay so much more hehe
1. If you want to buy the cheap luggage (less than 100 dollars) then you get what you pay for. It's commonly called "one trip luggage" among those who sell it, and even those who buy it. I've had the reps come out and refer to it as one trip luggage. Those 3 and 5 piece sets for 80 dollars? Yes they're cheap, but by the time you get off the plane, they're destroyed.
2. My two favorite brands are Ricardo and Travelpro. Travelpro was created by a pilot, and is really made to withstand traveling. However, on the same level, Travelpro is quite a bit more than Ricardo, and I think Ricardo is just as good

The material used on the outside by each is exceptional, and the corners have an extra boost to them to keep them from getting damaged.
3. If you don't find a Ricardo or Travelpro (or want another brand), or find something on Clearance, here's what I look for. And don't knock clearance, I just got a $300 piece for $30!
*Look for a luggage that's originally priced around 260-300 dollars. I know people think you pay for name, but it really does make the difference in luggage. You can often find these on sale for 50-60% off at places like Macy's, and sometimes you can find them even cheaper!
*Look for an outside material that's like ballistic nylon (I prefer denier ballistic nylon). Look at how tight the weaving is on the material. Is it tight and shiny? Or dull and loose? You want tight!
*Look inside to make sure you get the right features. One thing I like in my luggage are the removeable pockets that I can use to throw my toiletries in. Ricardo's that I've purchased and sold all had a plastic bag that attaches to the luggage, and unattaches when you want it to

Love that feature!
*Feel the bottom of your luggage from the inside. Many types of luggage don't pad the bars that hold it together. My luggage all have a bit of padding there, so if something hits it, it won't break. Yay! And hey, I've transported a ton of glass items, and never had them break

*Look at the different compartments. One of the best features of Ricardo is they have a "Dirty clothes" section, which has plastic on both sides instead of cloth. This allows you to put those dirty wet clothes in an area that won't get the rest of your clothes or items dirty! Yay for that!
*Check out the garment bag. Many different luggages have a section inside the luggage to hold your suite tops, etc. The Ricardos have that section as something you can remove and hang up in the closet. It's made to generally fold in 2 or 3, depending on the side. If you look at the piece itself, they usually have padded sections where it folds and to hold it in place, and then a zipper enclosure to keep the clothes neat. I can't recall what other brands have this, but I really do like it. Other luggages just have a piece that folds and another piece that goes over it to keep it in place, and that doens't work as well. The clothes fall out and get wrinkled asap.
*Check the corners. They should be reinforced with SOMETHING. The stronger the reinforcement, the better. Travelpro and Ricardo each have a hard plastic around every corner, and this keeps it from getting banged around.
I guess the biggest thing I cannot stress enough is you DO GET WHAT YOU PAID FOR. Just remember that; if you want to take a shortcut and go cheaper, you'll end up buying new ones constantly! I've had my luggage for 4 years now, use it frequently in flying, and it still looks brand new. The only problem is where I had a lock on one of the zippers (NOT locking them together at all, it was just hanging there) and the FSA busted it off and put a note in it saying that I'm not suppose to lock my luggage! I've had my luggage sit out in the rain and I picked it up completely soaked. I was afraid everything inside would be wet, but it was completely dry
one thing I've seen that seems interesting to me, but I was done selling luggage by the time this came out, are the wheels that rotate 360 degrees. If I was buying another piece of luggage, I'd definitely look into this luggage and see how I like it
That was a lot of stuff, but I hope you get at least one thing out of it

Good luck with your luggage!!