If you want to heat the space as well → check the thermal output (Watts) and the size of the radiator, not just the design.
If the bathroom is small → pay attention to the width and wall projection, so it doesn’t interfere with movement.
If everyday practicality matters to you → look at how many bars it has and the spacing between them, so towels can hang and dry properly.
If you only need towel drying or don’t have a central heating system → an electric heated towel rail is sufficient and works independently from the home’s radiator system.
If you’re considering a black towel rail or a stainless steel (inox) bathroom radiator → choose the one you like most. Both have pros and cons when it comes to cleaning: black finishes are more sensitive and show limescale easily, while stainless steel tends to show fingerprints.