Best tool for Agricultural Vehicles diagnostics/Motor hours correction.

Hallo,
I wanted to make some research. Can You tell me what tools you use and what is the best tool I can buy, for Agro vehicles?
Diagnostics, Motor hours correction ... etc.

I am interested in particular:

New Holland
John Deere
Landini

Thank You,

P.S.
Sorry if i repeat old threads maybe You can point me in the right direction.