Both formats have different crop ratios, each adapted to specific sources. If you’re shooting with your phone (of any brand) or with a Micro Four-thirds camera, the default aspect ratio is 4:3. Our Regular format was specially designed for these cases. If your using a Full Frame, APS or APS-C sensor, the default aspect ratio is 3:2. In this case, we recommend using the 10x15 format.
Using the right print format will make sure that your image is printed without the need to crop it (unless you’re using a square format).
If you're not sure about your device's crop ratio, please contact us so we can help.