SDC, not exactly sure how the addition of "A" and "D" is arranged (presumably the airline planning sections looks after it) but I don't recall it being stuffed up.
I've never worked tower, but I've spent enough hours watching to know both en-route and tower can have their moments. Both operate along the lines of "90% boredom, 10% terror" plus or minus.
Many of the towers aren't 24 hour operations (regional, secondary, GAAP) so if you go tower you may not work night shifts but may be posted all over the countryside. Whereas if you go en-route you'll work nights eventually (once you have enough ratings) but will stay in Melbourne or Brisbane.