I have run the ATR liquid intercooler on the T Type for 25 years. That intercooler has been used on a number of turbos, the biggest one is in my signature.
I do see a difference of about 15 to 20 degrees drop in air temps versus an air to air unit. The IAT is mounted in the back of dog house on the throttle body so I have logged it.
For street use the liquid intercooler keeps the air temps low around town with no problem. I do see better throttle response and spool up using it. These days especially, a good air to air unit will do that too.
I can tell you that the air temps in summer are kept lower because of it. And in winter the car loves the cold air more so than most.
I do know that the intercooler gives me good repeated results on the strip as well. Back to back runs have shown the same temps again and again.
ATR was the only one that made a liquid intercooler and they have been long gone. ATR quoted efficiencies of 80 to 90% using it and that is pretty accurate.
Keep in mind that 25 years ago we were looking for ways to get the most performance out of 92 octane gas and this was one of them. The fuel became the limiting factor no matter what we did. The other option was race gas on the street and no one was really doing that because the O2 sensors would get fouled up the minute you put race gas in the tank.
The solution to that has been Razors alky kit and or E85. Which I am seriously looking at doing on my car.
The liquid intercooler works and there is no downside to it in my opinion. It is a self contained unit with its own pump, heat exchanger and intercooler.
It will come down to personal preference and availability for most people.