It's based on what type of content you're expecting from the user
Text has the capacity to hold 65,535 characters which is about 64 KiB of size while LONG TEXT has the capacity to hold 4,294,967,295 characters which is about 4GB of size.
Is there any performance of memory penalty for defining mediumtext instead of just text? I may go with mediumtext since I do not know in advance what enduser may decide to put into the body of a blog post for example documentation which could be as large as 50 pages book etc. What do you think of mediumtext for such a case @samalapsy ?