While you think about the question, here are the modes in question.  The text below was taken from our own lovely Geometry Wars 2 page.

Deadline

In Deadline you will have 3 minutes to score as many points as you possibly can.  You have infinite lives, however if you die a lot it works against you.  If you pick up Geoms which can be picked up off destroyed enemies.  By picking these up you can increase your score multiplier.  It’s possible to get your multiplier past a thousand.

King

In King you can go into these circular zones that will appear on the map.  Once inside you can shoot out of the zone, but if you stay inside to long they will collapse thus destroying you.  Collect Geoms once again to increase you score.  This mode is available in co-op play.

Evolved

Like Geometry Wars: Retro Evolved this mode gives you three lives and three bombs.  However this mode has changed from the old game.  There are new enemies, along with just being able to use one weapon.  Gravity wells will destroy enemies when they explode.  They also changed the scoring system so that after you get 100,000 points and your extra life and bomb the next time for an extra life or bomb will increase 10x that amount and thereafter.

Pacifism

In Pacifism the object is not to shoot anyone, but instead move these blue shapes through gates that will explode and destroy your enemy. 

Waves

In Wave you will have just one life and no bomb.  The object of the game is to survive as long as possible as each wave gets stronger and stronger.  One achievement is to survive 8 waves without firing a shot.

Sequence

In Sequence there are 20 levels and the object is surviving all 20 rounds without dieing.  Each level is only 30 seconds long and you must clear it in 30 secs or less.  Also if you die you don't gain points for the level, but move onto the next.  One good thing is that on each level every guy respawns in the same place.

I think I'm looking forward to Sequence and Deadline the most.

I like sequence the most

I freaking want to play all of them!