I believe the different comp types all cater to a different kind of player.
Rakeback is something that regular players will be interested in. Loyalty programs are mostly beneficial to regular players as well.
For the bonus whores, poker bonus codes will be at the top of the list. Rakeback and especially loyalty programs aren't as important because they don't stay at the same site for extended periods of time, and at most sites, bonuses are deducted from rake and rakeback.
Finally, a no deposit bonus is a great way for play money players or new players to get their feet wet at the cash tables. Obviously these no deposit bonuses are generally quite small. However there are a few free bankroll offers that will start players off with up to $150 cash at several poker rooms.