There are a lot of generic kits to choose from, and a lot depends on your ability to install the kit, and how complete the kit is for mounting specifically to your tractor. Kubota makes a kit that is specific to your tractor, and the upfront cost might be more than the generic kits, however, when you have to start buying parts to adapt the kit to your specific tractor, the cost of the generic kit can actually become more expensive than the kit that was designed for your tractor. Over the past week, I have been doing a lot of research on the subject, and for my tractor (BX23S), the Land Pride kit that is specific to my tractor is a better buy than some of the generic kits available. If you are going to be installing the kit yourself, I would be more inclined to go with the tractor specific kit, if for nothing else than having the support of the Kubota dealer that sold it to you. Since Land Pride is a wholly owned company of Kubota, and they are offering Kubota specific 3rd function kits, I believe that the Kubota dealers that are selling these kits also have the same factory support, should you run into a problem. I went to the Kubota build a tractor website, and tried to figure out what a kit would cost for your tractor, and there were so many different ways that the loader valve could be configured, I believe that you would be best off if you were to discuss this with your dealer before purchasing anything. Keep in mind that if you should install anything on the tractor that wasn't approved by Kubota, should you have a failure in the future, that might be a reason for Kubota (i.e. The dealer) to deny the warranty claim. Just one more reason to stay with factory approved accessories. You spent a lot of money buying your tractor, and now isn't the time to start cheapening out of buying functional improvements. You can do that with mowers, grapples, etc., but not with the tractors hydraulic system.
These comments are my opinion, and others might agree or disagree, but it is clearly your choice, and in life, we are all responsible for our own choices in life, good or bad.