Is there a reason that a new 610 (big) series kitchenaid would need to be used differently that one of the regular classic kitchenaid mixers?

My girlfriend just bought herself a new 610 Kitchenaid mixer. She had previously been using a classic series one. She made several batches of swiss meringue butter cream frosting in it (the only ingredients of which being sugar, egg whites, and butter), and it came out not stiff enough for piping every time.

Is it normal to need to mix things differently for this series, or should we look into returning it?

Side note: It’s also really loud. Much louder than the classic series.