I take a lot of screenshots on a daily basis for various uses, so I make sure I use the best tools for this purpose.
Here are the various options out there.
Mac Inbuilt Screenshot Facility
Your Mac comes with an inbuilt screenshot facility that is accessed via keyboard shortcuts. If you use Dropbox, you will also get prompted to automatically save screenshots to the Screenshots folder on Dropbox, and a link to the latest saved screenshot will be copied to your clipboard, so you can instantly share that image with others if you need to.
If that covers all your needs, I don’t see any reason for using any apps, just learn the few shortcuts that you need and you’re good to go.