I just got my first Linux computer which came loaded with Ubuntu 18.04.3 LTS. I don't like it. I had them load Elementary Juno (5.0) onto a USB drive for me because I had already decided it was probably what I wanted anyway. I am installing Elementary and it's asking if I want to dual boot with Linux or wipe it out completely. What I want to know is if there is any advantage to my keeping Ubuntu as a dual boot or should I just wipe it out? If I dual boot it I can change the allotment of memory but it says that it can't be undone. If I do dual boot should I allot Ubuntu less or keep them pretty even? Thanks, in advance, for any help with this. I have Googled it but I'm a little out of my league right now.

No if your not interested in dual booting. Just make sure any files that is important to you is backed up as you will loose them when elementary overwrites the ubuntu system.
Are you talking about disk space. It would be hard to say without knowing the size of your drive.