WHAT TO CHOOSE

The HDI3000 replaced the UM-9HDI and will therefore be a newer system. If both are working correctly with good probes, the HDI3000 will have better image quality. It will be nearly impossible to find parts for the UM-9HDI. It will be difficult to find parts for the HDI3000, but there are still some out there. 

THANK YOY VERY MUCH

IS THERE COMPATIBILITY BETWEEN THE PROBES OF THESE TWO MODELS OR THEY USE DIFFERENT ONES?

There are a few probes that run on both the UM-9HDI and the HDI3000; L10-5, L7-4, C5IVT, C4-2, C7-4, the CL10-5 (part number 4000-0315), and the 2 MHz AuxCW and TCD probes.

Have you considered getting another Logiq 7, or a Logiq 9 as your back-up unit? They are one generation newer than the HDI3000, and parts and support are much easier to find. You already have probes that will run on both systems and since the probes are worth as much or more than the systems, the total cost might not be much different.

I would stay away from the UM9 since it is ancient and support is very limited. Jim Carr is correct that another GE would be a good idea. I am not a fan of the Logiq 7 due to support and reliability issues but a L9 is a great choice and is very inexpensive since you could move probes between both systems.