Choose the one you like the best. I prefer the lower rad hose style. Other people go for the frost plug style. If you are doing it yourself then choose whats easier for you to install.
Based on my experience the block eater that installs in the engine water jacket is the best type. It's relatively easy to install and puts the heat where you need it which is in the water jacket. Rad hose heaters are useful if there are no core plugs in the block but some of their heat ends up in the radiator.
Consult with someone like your local Kubota tech about location to avoid confusing the temp sensors that go to the ECU and affect starting parameters and dpf operation.