Since this is the Welcome Center, I am talking a little bit of liberty to think that many coming into this group have not had a lot experience with Jira and creating new projects. I know this is the Welcome Center for Community, but I also see lots of people new to the product.
I am also seeing many people asking questions about how to do this thing or that thing in a particular Project type in Jira. This is not intended to be an all knowing information burst for deciding which one to use, but more of a helpful encouragement to research each project type in view of your end goal with the project.
Yes, Next-gen projects are easy to setup and use. But you pay a price for that with little customization and flexibility. If you know your team or organization likes to do things outside of the box or likes to have things their way, Next-gen is probably not the path for that team. I would lean towards a Classic Software project.
However, if you want something simple without needing to learn all of the ends and outs of Jira (which can be complicated), then give the Next-gen project type a whirl.
Business projects (Jira Core) fit neatly in between. You can have shared schemes and shared custom fields, etc., and have some control over the workflow. But you cannot have multiple issue types in the workflow scheme or your board will fail. And there is little customization of the board.
In conclusion, PLEASE research the project types before you commit too fully to one style or the other. It will save you heartache in the end.
Cheers and Saludos!