Breast milk freezer bags are a necessity for a nursing mother. Even if you are a stay-at-home-mom (SAHM) like I am (long story, the job didn't work out), you still need to pump, even if just for comfort reasons. There is no need to pour out perfectly good milk so why not freeze it?! If your freezer becomes overly stuffed like ours is at the moment, you can always donate it to the Indiana Mother's Milk Bank, IMMB.
When I first started pumping, I used the Medela bags simply because I had a Medela pump and you can pump right into the bag; no need to clean bottles every time. Well, then I learned that you usually want to combine the two sides of milk into one bag or bottle anyways so you're going to need to do dishes. I had some Lansinoh bags as a sample pack and started filling those too. What a difference a bag makes!
So on the left are the Medela bags, and the right are the Lansinoh bags. Immediately I noticed the bag size difference. The Lansinoh's are much longer and have a higher storage capacity of 6 ounces (versus only 5 ounces with the Medela).
Pricing comparison? There is no comparing ... Lansinoh is LESS THAN HALF the price of Medela for the exact same amount of bags, 50-count. Medela is expensive, running about $20-23 per 50-count box. Lansinoh is only $10 for a 50-count box.
When comparing the ease of writing on the bags/labeling there is a big difference too. Labeling is labeling, I know, but per state regulations (if you're using daycare) there are four things you need on each bag: Name, Date, Time and Amount. Although not a large space, there is space for each of these four items on the Lansinoh bags. The Medela bags do have a large writing space but it's totally blank; so I guess that could be a possible advantage.
Also you will notice that the Lansinoh bag has a seal at the end of it. You just rip that off (so you know the bag's never been used and is clean) and fill it up.
The seal is very very important when freezing milk. If the milk gets freezer burn (hey, it's happened to the best of us) then you've got to throw it all out. Also, if there's a leak it can make the milk go bad quicker. Note: If it smells funky, don't use it. The Medela bags have been known to leak (and I've experienced this as well as freezer burn). The Lansinoh bags have a double-zip seal so that is less likely with those bags.
With either bag (or any other brand), DO NOT overfill them or you will almost guarantee yourself a milk explosion in the freezer.
Both bags are able to stand in an upright position, although Medela has the advantage here since they are more sturdy. Why you would need your bag to stand up .. I can't tell you since I have no idea. It is nice, though, when first starting out and being able to pour it into the bag on the counter top.
So when the bags are laying flat, which is the best way to freeze and safe space, the Lansinoh has the (obvious) advantage. It lays much flatter, hence the longer/larger bag design. They do tend to stick to one another easier, though they aren't hard to break apart once frozen.
And finally pouring is extremely important! You've got to be able to pour the milk from the bag into the bottle when you need it. Medela has a hole cut out of the tops of their bags, but the milk bypasses it and I often get half of it on the counter tops. The plastic is very thick on their bags so it makes it hard to pour any other way.
The Lansinoh bags, however, don't have a pour spout but the design shape of the bag allows for you to pour it out of the sides very easily with minimal spilling.
The Lansinoh has the best advantage when it comes to: price, storage capacity, labeling, sealing, space-saving, and ease of pouring.