If I was playing the game I would like levels. Developing a game, I would think levels were good. You could make a storyline too.
for example flight control and other games doesn't have levels ... but they are interested.. and we don't know really what would be better
Best is to include both mode. As survival mode is what the users will be playing after completing the level mode. Not many would run through the level mode twice once they are done.
I like challenging levels with good balance, levels that you will have a chance to win but still so challenging. e.g. The last level in "7 Cities", I win after I played over 50 times.
I have both in the game I'm currently working on. The game is survival, but as you survive longer and longer you level up and get new unlocks.
