Start with two separate notes
Give each pair one note for toe space and another for underfoot feel. A soft first impression can distract from a front seam or a foot that keeps moving forward. Equally, a roomy outline says little about the cushioning you prefer. You need both observations to compare a plush house slipper with a molded slide fairly.
Read what is inside the sole
Look for the stated insole and outsole materials. Memory foam describes a material, not a standardized level of softness or a promise of how long it will feel the same. A thick-looking sole may contain several layers. If the listing does not say what those layers are, record that as unknown. Marketing terms such as cloud or pillow do not supply the missing construction details.
Compare your ordinary indoor steps
If the return terms allow it, try the pair briefly on a clean indoor surface representative of where you will wear it. Notice whether the underfoot feel suits you and whether your foot stays placed on the sole as you turn. A tread pattern or a claim of grip is not a guarantee on every surface. Do not test slippers on wet floors to establish traction.
Consider the whole pair before modifying it
An additional insole may raise your foot into the upper and reduce space above the toes. If you expect to change an insole, confirm that the original is removable and ask about the remaining depth. Keep your usual socks in the comparison too. A pair that works only with a different sock thickness may be acceptable, but it should be a deliberate choice. When two candidates feel similar, compare the clearer fit information and the return terms before being persuaded by a thicker sole in a photograph.