I find the Milviz T-38 instruments to look a bit more realistic, as I remember them. However, for the life of me I can't get it to start from C&D, the huffer only shows briefly then disappears. Dimus gave me some ideas to try. Tried them but they didn't work.
The Infinity T-38, which is built by Aero Dynamics is actually two birds. It offers the "C" model. If you like HUDs, this is your jet. I find this "A" model instrument panel's graphics to have slightly less fidelity than the Milviz's model. However, that isn't a deal killer for me. After a couple minutes, I quit noticing the difference, and I think that only someone who has flown the actual airplane will be aware of any differences.
What I do like about the Infinity model is that via the checklist, found in the map case, you can have external power and air provided, complete with a crewchief's voice. it was almost deja vu for me to go through the start up sequence. What I don't like is the stupid tablet holder on the left that you can't remove. Never had them on the real jet, at least not in my day.
Both need fiddling with the controls. I found the pitch to be to sensitive. I use a curve to dampen the pitch in the early stages. Did the save from the roll, although it wasn't as bad. With the Infinity model I had to assign a button for the afterburners. Thankfully the Winwing throttles have an afterburner (reheat for you Brits) built into the AB detent. I just had to assign them to the AB's. Set them as a toggle, so they come on and off as you go though the gates.
I have not tested either of the versions to see if they follow the curves. Since I was involved with developing the original Milviz T-38A I knew it flew by the numbers. I assume this version does too. The Infinity version feels good to me. Infinity claims their jets to be at least simi-studly level. I will give them the benefit of doubt that it is close to the real airplane's numbers. I do know that the "C" model systems are complex. They even offer simulated bombing and AA, just like the Robbins AFB fighter intro models do.
As for which one to buy, in my opinion, unless you are a tried and true steam gauge guy who will never fly the "C" model, I would go with the Infinity model. To me the "C" model is worth the extra money. Aero Dynamics is still developing the two models. What you are buying is a highly polished Beta.