I have had poor results with using 2, 3 or 4 mi Uline bags for vacuum sealing. My best guess is that the bottom seal of the bag is not wide enough to ensure a good seal. I do not understand why, because the bags do hold water but I have numerous failures both right after sealing and after several days later. As a part of my occupation, I use a large chamber vacuum machine for packaging of product for resale. Even after first heat sealing the bottom of the bag with a traditional heat sealer which can affect the product appearance (important for retail, more than home production), and than vacuum sealing the product the vacuum holding failure ratio is still unacceptable.
I have flat vacuum seal bags that I use for my machine, and I stock (for resale) the bags for the foodsaver type machines. Flat packs of the foodsaver type bags can be purchased for less money than the branded rolls.
Uline bags work well for non vacuum heat sealing, as well as twist tying bags shut. They always have an excellent selection, and quick shipping. However as a person who's employees use several thousand bags of various sizes a month in retail (most 2 mil), there are other places to purchase bags at lower cost.