Here's my 2c, I have only done one project with FT ME, there were 2x 10" screens, plus a 6" developed by another company that I had to modify.
I started off with a tag database, but then found during startup that the memory was getting low reasonably often, and coming up with an annoying windoze error message.
Then, it became a task to update the application due to low memory issues. Cycling power was the way to overcome this.
I then looked at direct referencing, and found that not only did they update faster than the tags that were in the database, it also helped to reduce the tag database size, therefore overcoming the issues I mentioned above.
I do still have a certain no of tags, for the purposes mentioned above, such as trending & Setpoint limit entry etc, and also for some descriptions, but that is it. The reduction in file size was a huge benefit, as was the faster update. I do agree about the portability & single point of modification etc, but in this instance I had to look at an alternative option.
We have since upgraded the terminal CF & Ram to a larger model, so the tag database size may of not been as much of an issue now, but I am sticking with direct referencing on this project, & if we do another one, would probably do it again.