If your builds aren't doing anything particularly challenging and everyone on your team is using SlickEdit, then I'd favor SlickEdit's built-in build system.
Where external make systems really shine is if you have extra steps, like pre- or post-build processing that you need to do. Also, if your team is using a mix of tools, an external make system will provide consistency to all team members to ensure that builds are done precisely the same way. It also facilitates setting up an automated nightly build process, which many consider to be an important step in a well-managed coding process. You can do that with vsbuild if you prefer to use SlickEdit's build system.
We try to be process agnostic so that you can do things the way YOU think is best. If the SlickEdit build system makes your life easier, by all means you should use it.
--Scott
