When looking for an inflatable Jumping castle Manufacturer always look for quality. You want your inflatable to last a long time. The manufacturer should use top quality products for your investment.
Second consider the manufactures range. The larger the range to choose from the longer they have been doing this. That more than probably means they know what they are doing.
Thirdly, consider if they are able to custom make a Jumping Castle for you. This will translate to experience, expertise and resources within the company.
Fourth, consider after sales support and maintenance. If you can secure a maintenance schedule or at least have someone in the know that you can build a relationship with. If you get on well, you can have a great rapport when it comes to fixing and maintaining your investment.
Also look into the option of delivery to your area. What about testing the Jumping castle once delivered.
Also consider renting a Jumping Castle to check out the quality before a purchase.