+1 to what Irwin said above.
Two thoughts from me. The non-technical answer: There are people who swim in the arctic circle without wetsuits…and there are people who refuse to get in pools unless the water is 80 or above. Whether you wear a wetsuit on race day should probably depend on where you fall in that spectrum :p
The technical answer: as a former college swimmmer, I’d recommend it since you’ll be faster in a wetsuit than not in one (all else equal). There’s a reason that FINA started banning suits for pool competition that were made with similar rubber/materials as wetsuits and that’s because they were buoyant and, therefore, fast. That said, it’s hard to make ‘all else equal’ on race day so, like Irwin said, try one out and make sure you’re comfortable and used to the way you feel in a wetsuit as it’s different than not in one. You’ll float easier and likely have less drag assuming it fits correctly. That should be faster but if it’s an abnormal feel on race day can throw your stroke off more than actually help.
If you want some interesting research on wetsuits and their advantages, see the below link. In a shorter distance race, you won’t gain much of an advantage in a wetsuit beyond staying warm which, to be fair, can be valuable if it’s really cold water. In a longer distance race though, the evidence begins to suggest that wetsuits help reduce drag and make for better body alignment in the water, thus improving overall performance. Still, based on the study’s results and their lit review, those benefits tend to show up more so for women than men, and more so for more inexperienced swimmers than those with better form.