Is there a better app to create Entity Relationship Diagrams than the Sql Server or mySQL studios?

Awesome! Thanks for the suggestions and links. I'm going to try SQL Power because they have a download for Linux. Would you say there are specific features that should be prioritized for ERD creation?

I'm not sure if you mean are there certain things that should be prioritized on the ERD itself, or that should be prioritized as features of the ERD program. I'm going to assume the latter, as I have no way of addressing the former for your use-case.

If a tool is standalone, I look for it to have specific value-added to my diagram and schema creation over what's already provided in-house.

For example: does it allow for automatic creation of PK/FK links? Does it allow for showing a table's indexes (which in special instances can be useful to have shown on an ERD, such as when using full-text indexing)? How about showing when a column has default values (or allows nulls)? How does it handle the display of synthetic (auto-computed) columns compared to actual data columns? Does it tell you when the table has a trigger? Does it tell you when a table is mirrored in Change Data Capture?

Many of these are things you only *rarely* want shown on a diagram because they can overly clutter things, but when you want them shown, you *really* want them shown. I've never seen a tool that does all of those, and many don't even try at *most* of them because those items I mentioned are all rare enough that we all have an assumption in our heads about the minimalist ERD and the tools tend to conform to that thinking. But if you do find that you need one, and prioritize those features based on your unique use-case, it can provide a powerful basis for comparing different products.

If you wanted an absolute top feature set, though, just make sure the look of the resulting diagram is clean and conforms to how you want to display data in the first place. ERDs often exist as part of a larger documentation set, so make sure that it looks appropriate for that task, which means going up to management and becoming a permanent part of the project data rather than just a developer aid hanging on your cubicle wall. Also, what is the diagram export options? Does it allow you to port over to MS Office Visio for merging with other data? Does it allow you to copy/paste into a PowerPoint as objects that can be moved around rather than as a screenshot?

And again, I've only worked with a few over the years. My preference is to stay as close to the IDE as possible. Your mileage may vary.