Most scheduling software is built for companies with dispatchers. If you are one person, or two, most of what you are paying for is overhead you have to work around.
It has to stop double bookings on its own
This is the whole job. If a customer can pick a time you are already working, the software has made your day worse than a paper diary.
The check has to happen on the server, and it has to account for how long the job takes. Offering a three hour deep clean at 4pm when you finish at 5pm is the same bug as a double booking.
Your clients should not need an account
Every account you make a customer create loses you bookings. They should open a link, pick a service, pick a time, type their details and be done in about a minute.
It has to work with one hand on a phone
You will use it standing in someone's kitchen, not sitting at a desk. Today's jobs, the address, tap to call, the checklist and the button that marks the job done all need to be reachable without pinching and zooming.
Repeat clients should be automatic
The steady money in cleaning is the fortnightly regular. If the software makes you enter that booking again every two weeks, you will stop using it by the second month.
You should be able to get your data out
Your customer list is your business. Any tool that will not let you export it is holding it hostage, and that should be a dealbreaker no matter how good the rest of it looks.