I was at the same cross roads when I installed the aaz into my samurai......
Install an rx7 oil cooler with thermostat sandwich adapter, or install the [ larger ] Passat v6 vw oil / water cooler heater. Which to do......??
For my Pacific NW climate, I decided to go with the Passat v6 cooler/ warmer. Why? IMHO, more engine damage is done with cold engine starts and thus I figured that the faster the engine warms up to operating temps, the better the longevity of the engine should be. Will the oil get too hot come the 30 deg summer days? Dunno. I'll find out I guess.
A worse scenario [ in my mind ] would be that the oil never really warms up to 180 deg. or, it takes forever to warm up to 180 deg.
Of course......you could install both....an oil cooler AND the larger v6 oem cooler / warmer. That's lots of plumbing in the engine bay......something I didn't have room for.
Make sure you have adequate rad cooling. Don't scrimp on a cheap / inadequate rad. If that's compromised, you're not going to be able to cool the engine [ or the oil ] adequately.