Understanding agents selecting among markets
If a market has free entry, then profit will tend to zero in the long run. Monopolistic competition and perfect competition are both characterized by zero long-run profit. Of course a firm would prefer to enter a market in which long run profits can be earned, but such markets are characterized by barriers to entry. 

To better understand this, consider a market in which firms can enter with entry cost $c$. Then, in long-run equilibrium, the profit that will be earned by incumbent firms cannot exceed $c$, otherwise potential entrants would have an incentive to enter the market.