I did both.
As others said, IMoo was a lot colder and a lot more windy. The rain started just as I got out on the bike at IMoo. It was mostly just steady throughout the day, with periods of no rain. It did pick up again on the run with more wind.
I was aware of the forecast and packed arm warmers and a beanie for the bike, both of which I used. I also borrowed a cycling trick and put vasoline on my legs. I was fine on the bike by staying in the aero position and not stopping with the one exception at the bike special needs. People who stopped for porta-potties or mechanicals were doomed to hypothermia.
For both races, people found out that they pee a lot more on the bike in cool and/or wet conditions. This causes constant lines at the porta-potties, and further increases the likelyhood of hypothermia setting in. For me, I was at the fine line of comfortable-cold. If I had stopped, I would not have gotten warm again.
In T2 at IMoo, I had a technical tee in the bag which I put on underneath my tri top. I also kept the arm warmers on, figuring I could roll them up and ditch then later on at special needs. I rolled them up after about 2 miles, and rolled back out after a couple of more miles.
The finish area at IMoo was a shiver fest. You couldn’t make it past half a slice of pizza before it got uncontrollable. The wind was still whipping and it was still raining. I passed on hanging around to watch the late finishers. I just wanted hot food, warm, dry clothes and no wind.
For LP this year, I went without arm warmers and the vasoline. I had a Chrono aero helmet with just a few vents and the De Soto Cool max cap. My head stayed dry until well into the second bike loop. To me, I thought the air temp was around 70 and quite comfortable. Still, after I finished, I got one slice of pizza down and then the shivers started. So, it was time to clean up a little, get the massage and change into the dry clothes. Met the wife, went back to the room, showered, changed, held onto the mylar blankets for later and then off to the LP Pub for a cheeseburger and a beer. Back to the finish line and watched and cheered for the rest of the night.