If you want to find out which interface/stabilizer works best for making handbags, you should pick up HEAVY CRAFT STABILIZER, PELLON 70 or PELLON 71.
Walmart sells heavy craft interface/stabilizer for ~$4.50/yard. You can also get the heavy craft interface from Joann, (I think it is Pellon 70) price at $5.99/yard. Although, Joann seems more expensive but you can usually get 40% off with the Joann's coupon.
The one from Walmar and Pellon 70 works really well for tote bags or small handbags, but if you want something really firm then you need to use Pellon 71 from Jo-ann.
Pellon 71 is the one-sided iron on (heavy craft) interface, Joann is selling it for $7.99/yard. Somehow the glue on the iron-on surface gives it extra firmness. However, if you try to iron your fabric onto the Pellon 71, you'll notice that the bag or fabric will become creased or wrinkled. To prevent the crease/wrinkle I SEW the fabric onto the interface, I DON'T Iron the fabric onto the interface.
You should try it and see the difference...