All chess clocks time the match. Some just time, some add delays, some add on, and other have variations for TIMING.
What else might be a factor in deciding to buy a clock that is primarily for personal use at speed chess in a club, cafe, or park, but also useful should one play in tournaments? For examples, cost, reliability, and ease of use are some factors. What would be the features that would help guide a purchase?
There might be other subtler ones, so a complete list for consideration is what is asked for. Comments on why would be useful too. EG what value does some certification add, if any.
I am thinking there could be easily a dozen or more of these NON-FUNCTIONAL characteristics.