Tech2 is the most cost-effective one, for it is with reasonable price and covering not only For GM vehicles, but also For SAAB,For OPEL,For SUZUKI,For ISUZU and as well as For Holden.
Besides, it is with authentic For GM software and support on-board diagnostics on all gm systems. If you want to use it to do For GM car programming, you should buy tis2000 software.
One disadvantage is that tech2 remains an basic or essential gm diagnostic tool for vehicles before 2010.
For GM MDI is used to serve vehicles with auxiliary CAN bus that cannot be served by tech2. Actually, this car diagnostic tool is working with vehicles after 2010 and covering newer models than that of Tech2.
Its highlights are with faster reprogramming (increased about 20-70%), serving exclusive new models, and more economical. This is a good investment for future vehicles models.