Nexiq 1 is discontinued. no more updates but for most people it will still work just fine.
Nexiq 2 is the current model and has more future potential than what the nexiq 1 could do.
Cables for each are different so they are not interchangeable. When ordering, you should make sure you get 3 different cables. The standard 6/9 pin y-cable with the green connector on the 9 pin plug so you can communicate to the newer 500k baud network. A standard OBD II cable and an OBD II Cat cable to talk to Caterpillar engines in GM trucks. If you need to communicate to trailer ABS, you will also need a PLC adapter.
Do NOT buy the inexpensive clones that normally come with multiple cables. The clones are not reliable and if they update with nexiq software, they will become a brick.
The nexiq 2 clones don’t have 26 pin cables just the standard fitting also the usb connector is different and there is a hole by the usb connector on the clones as well.