As a cleaning business owner myself I can obviously verify that all cleaning companies are not good.
Personally we are very good in general but occasionally make a bad hire who will not follow our training and, much as it grates on me, it is par for the course while we are attempting to bring that cleaner up to our standards a client may receive poor service the odd time. What matters is that we correct this straight away and send a new cleaner plus if that cleaner refuses to or cannot improve we have to let them go, as much as we need the staff. This does not happen often but it happens within any cleaning service. Not every hire will be a good one, it's how the company manages the situation when it's not great which determines whether they are offering a 'good service' or not.
As for private cleaners it seems they are always a gamble, as a self-employed operator they will manage themselves how they see fit. Nobody is there to train them and they usually have no complaints systems in place so how they handle these can be random. I've even heard of angry responses to complaints from individual cleaners and there is obviously no management to go to.
On the other hand, although it's a much more random process if you do manage to find a good solo cleaner then I would stick with him/her until the end of time (or until they stop offering service whichever comes first haha!)
When we are called in after clients have suffered dissatisfaction with a solo cleaner before us the thing that caused the most dissatisfaction was the cleaner not honouring the regular booking and being irregular. Many times I am told 'She would more often than not just not turn up for the clean'. You don't get this with a company as they will have procedures for reporting absence early to arrange cover or reschedule etc.
In a nutshell a company is much more likely to have systems in place to make sure you are well taken care of because that is their business but not every service is well- run.
A private cleaner is only as good as he or she is, and if you are unhappy you must manage this with him/her yourself directly.
Obviously a cleaning company will need to charge more than a solo cleaner because of overhead and different services cost different amounts.
It all depends upon what your personal needs are and what each cleaner/company is offering to meet those needs plus depends upon your budget as to which service level you can afford.
You will find a good match eventually, it just sometimes takes time to filter through what you don't want first then you suddenly click with a service provider that has everything you need in terms of service level and customer service and is set up in a way that makes you feel comfortable.