The real difference is that the Re-Therm pouches are reinforced to be able to handle being boiled for a longer amount of time, up to 30 minutes. The other bags can be boiled, but not for that long without being compromised. When a normal bag becomes compromised, the pouch will begin to delaminate. A pouch is made of 7 or 9 layers of material (similar to the construction of a sheet of plywood), so after many hours of heat, water, and weight the pouch will begin to swell and the layers will simply come apart. Once delamination begins, the weight of the packaged food causes the pouch to break open.
Also Re-Therm pouches are great for if you're cooking sous vide, and cooking at a higher temperature. For example if you're cooking veggies at a high temperature like 185F+. If you're getting closer to boiling point, you'll want to use our Re-Therm bags.