I agree post flop. When the flop is down, if you have four cards to the flush and another player has an open ended str8 draw, the flush draw has 1 more out. Similarly preflop the chances of flopping an open ended straight draw with runners is 9.4:1 and a flush draw with suited cards is 8.1:1 however the odds of you being dealt suited cards is over 10: 1 whereas connected cards are 5: 1 approximately; giving you a fair old crack at hitting the str8 more of the time, not to mention gap connectors etc.
Hence flopping a str8 is 76.5:1 and flopping a flush is 117.8 :1, even with gap connectors the odds of flopping a str8 are better at 101:1.