Lots of people from Louisiana go during Mardi Gras. I've never been in October so I can't compare the two but I love Disney in February/March! There is really no slow time to visit anymore so there will be crowds but nothing crazy. The weather is unpredictable- could be cold, could be hot, could be both in the same day. Last year we went the week after Mardi Gras and it was one of the best trips we've ever had.