What's the difference between ING and IRR? Will I lose benefits, time in service, etc.?

If you go ING, your contract freezes. You are not considered part of the "active reserve." Once whatever circumstance that caused you to go into the ING is over, you will still have as much service obligation left as when you entered the ING. You cannot "complete" your enlistment in the ING.

If you go IRR, your contract does NOT freeze. You ARE considered part of the "active reserve" (Yes, I know what the I stands for, you are still lumped into to "active reserve" for this purpose). Your clock still runs and you can complete your enlistment in the IRR, and either re-up or separate.

One detail that is often overlooked, if you chose to go IRR (and the command approves), you will technically be separated from your state NG and become part of the USAR. I know that can matter to some people. State NG leadership will often prefer ING over IRR.

My understanding is ING is National Guard only and IRR is reserves only so dependent upon which you are is what you would be put into. I agree though that you should just finish out your time.

The contract will continue, you just won't accrue service points. If you go into ING with seven years, then if you were to ever come back from ING, you would still have seven years. I'm currently in that status and will be riding out my time.