Are there even any state associations that certify table crews? I have never worked a game with a "certified" table. In fact, the only level where I've had any appreciable issues with the table is the sub-varsity level. And at that level, there's no way you'd get anyone to work if they had to be certified.
The games where I've had officials I know working the table, the advantages were slight. Timely reminders about a team near the bonus/double bonus without asking, no clock issues, and knowing the table crew is as unbiased as the officials working the game. Again, nothing really that great. I guess one could have peace of mind knowing the table knows what it's doing?
As to what I prefer, in an ideal world, the table crew would be as "trained" and "certified" as the officials, but I don't really think it's necessary at all, not at the high school level at least. There's enough problems as it is getting certified officials to work all games. A quick pregame with the table usually means no issues during the games I've worked.