One more factor to consider is appreciation (guess)

Tax rate really high when one exercises employee stock option. 

Depending on strike price and whether one needs to use sell some sotcks to cover the option cost. 100 shares of stock (in call option) could yield only 50 shares or 30 shares. 

if stock goes up by say 20, 100 share can gain 2k, but 30 shares only gain 600. 

You are right on long term capital gain.