New wine vs old.
I prefer new wine..which is fresh grapes, not fermented.
Anglican serve port as their wine in communion services and I cant handle it, its very sour to me and got alcohol in it. Gives me a headache. I dont know what catholics serve, but if it is alcohol I cannot partake.
To be fair, a lot of parishes only serve the Eucharist in bread form, though the blood is present in wine form as well. Some people don't like the taste of course when they do receive, but they recognize that how it tastes isn't the point.