Are private hearing aids better than NHS?

You can always have both, Private aid as your main aid and an NHS aid as a backup, that is if the NHS will help. I have been to NHS Audiology and also have a private Audiologist in Harley Street. They both have Pros and Cons.
NHS Audiology - the main advantage is that they are free, plus batteries, repairs/replacements etc. The main disadvantage is the lack of choice - they will offer just 1 or 2 aids, and that is it, you can't say but I want a different manufacturer, different style. They are basic one size fits all models, with just 5 standard features in the same shell that you can get privately with far more features. They are 3 years behind the private sector. They are also very cheap, the NHS bulk buy millions of these for £50 to £150 per aid at this very basic standard (compared to £1k - £5k in the private sector). There will be no extra features or frills or bespoke engineering for you. Cochlear Implants will be £17,000 on the NHS but £60,000 privately. The service is also very bad. The standard wait for an appointment is 8 weeks, you only get 15, 30, or 45 min appointments depending on what it is for. They try to cram in 30 patients a day (in the private sector they see 8 patients a day). The main problem for me with the NHS is that they have a limited budget. They can only do x for x people. They will put their budget first, over and above your needs and have as good as admitted it to me. They have refused to give me the right aids for my needs, and will try to palm me off with less powerful aids that are in the band below what I need. And I have had to engage in major battles with them and put up with rubbish aids and rubbish service. I have heard many stories, for example in some areas of the country up north they will only supply 1 aid to people who need 2 aids, just to save money. 15 years ago they didn't supply digital aids, only analogue (as they lag behind the private sector) and I had to go private to obtain digital aids. This was such a massive improvement, wow, if only I had discovered the private sector earlier. Excellent service, excellent choice, lots of features can be added in, and they will custom build the aids for you. They are not ruled by a limited budget like the NHS and will put your hearing needs first rather than cost. If I ask for an appointment, they will see me next day, and they will devote an hour plus to chatting through my needs, and are so kind and knowledgeable. The main Cons are it is expensive, my aids are worth £5,000 plus per pair. But (Moneysaving tip alert) you can apply for funding via the 'Access to Work' fund through your workplace. You will have to be referred to the NHS audiologist first, then get a letter from them to say that they can't supply you with an aid sufficient for your needs (which often happens), and then you can apply for the Access to Work funding. Warning they have tightened up recently and the NHS don't want to write these letters, and they will do everything to wriggle out of it. (They now get a bonus if they don't write these letters). You will have to be firm with them. So in my opinion if you want the best aids for your needs go down the private route and apply through Access to Work for the money. Sorted!
Note: They've tightened up on funding and now will only pay 5/7ths of the amount and you have to supply 2/7ths, this is because you only spend 5 days in the workplace, and the 2 days at the weekend are your time. Some workplaces will help you out though depending on where you work.

Gosh, lots of issues here. Can I reply to a few?
You say the NHS has refused to give you the right aids for your needs, but that the private sector provides custom built aids.

This is how it works: you have a detailed hearing test afterwhich the results are used to digitally programme your aids. Left and right ears are programmed individually. It doesn't matter if they are private or NHS, it will be done the same way.
Your Harley Street doctor is able to give you a next day appointment because anyone with common sense has realised that they are only interested in money, and there is no queue. Just a few people who think it gives them some kind of superiority.