This is not a very good question. If you are concerned about security you need to think about what specifically you are trying to keep safe? Here are some examples of different security scenarios:
Do you want your computer to be safe when it is stolen?
Do you want to run lots of native apps from untrusted sources?
Do you want it to be used by many people and you don’t want them to be able to steal each others secrets?
Each one of those questions has different means of securing the computer. With question 1, it is not so much a matter of desktop environment, rather it has more to do with using full-disk encryption, setting a boot password in UEFI, and always having your lock screen enabled.
With question 2, this is a much more difficult task and you would probably be better off running apps in a VM, or carefully crafting your “Security Enhanced” Linux profile – or not using Linux at all, but using FreeBSD which allows you to run apps in jails.
With question 3, be more careful with filesystem permissions and access control lists, setup your sudoers file properly, and use a desktop environment with better security auditing like Gnome or KDE Plasma.