[GrandSport]

Water to oil isn't much use at the track. Your coolant temps are probably going to be around 240-250 so you're not going to get much cooler than that. Furthermore, it doesn't actually add any "net cooling." All you're doing is transferring energy into the coolant, not out of the powertrain system. So unless your coolant cooling system is very overbuilt, it's not going to do much.
Plus, in the event of failure, you don't want your oil AND coolant both overheating together, nor do you want coolant in your oil.

On a street car, water to oil is better because it cools better, costs less, easier packaging, weighs less and even warms up the oil faster. They are far more efficient, and the cooling system has plenty of cooling capability left for street driving- it's not stressed. On the track they can't cool oil down to anything below coolant temp. That's fine if coolant is 220 or so (ideal temp for oil, cooler is worse for longevity), but it's not very helpful if your oil is coming in at 300 and coolant is 250 and already stressed itself.

edit: obviously, if your cooling system is "overbuilt" and not stressed, it's a different story. Very few factory cars will run below 250 at the track when driven hard these days. Frontal area on inlets = big aero sacrifices. My grand sport is about the coolest running car I've ever owned, and it hits 240 or so easily. Keep in mind, it has the same cooling as its supercharged +200hp Z06 big brother (which, ironically, has inadequate cooling). It has ducts and scoops everywhere.