Each year my pony's get a check up. If they have something or not, just some prefention.
And yes it is quite expensive but it is worth it.
You have to find someone who knows what he or she is doing. Can explain what, why and so on to you.
So you can understand what happens and why. So you can see the difference before and after.
The person who comes for me, can do more then only osteopatie also acupunctuur, chiropractie so she can do the whole horse if there is something else which you can not help with osteo.
i can not say if it is better then a vet. It depends what the horse for problems have. Both works in a different way.
you can not compare it with each other.
What you can do also is "thermografie" (i dont know if it is the right english word) if you google you can find more info about it. That can maybe help you better in this case.