In the opinions above, there's been a lot of mixing between what's best for the program and what's best for the current team of players we have. However, in both cases, I think the NCAA tournament is better.
In looking at what's best for the current group of guys we have, I look at it this way: anything that's not an NCAA tournament game can't compare to an NCAA tournament game. The experience the guys would get, even from going one and done, would be very valuable heading forward. They would have a better understanding of how it works, what to expect, and what you need to do to be successful against a team that is fighting for their season in front of a national audience. I like to think that if they get a taste, they'll be even more determined to get back there and find success.
If the team gets to the point where they are NIT bound, that experience certainly won't be bad for the current team. As mentioned, learning how to win is something this young team really needs to feel and develop. The NIT, like a fringe bowl (for the extra game and practices), is good because it gives teams experience in a lower-pressure situation. But nothing compares to the NCAAs. The NIT is lower-intensity, lower-relevance, etc. No one cares about the 69th best team in D1.