I definitely simply prefer attack speed cause it makes it easier to get your q back and destroy turrets faster. You don't need E CD to be that short anyways, you'll mostly use the two extra levels to finish off minions that are out of reach. You also want to keep that minion wave on tower or freeze it in front until you hit 6. For sustain, you get hp back on minion kills + if you are in a poke matchup you simply get DS and sometimes if necessary second wind. So you shouldn't have any issue even against Kennen or Quinn. For most of these ranged matchups, you can kinda just go PTA and jump on em at 6 and they are so frail they just die.

As for Symbiotic, I'd say its up to whether you like to use them or not in the first place. I personally really like them cause it gives you insanely fast recall and you can come back to lane super fast. Also very good to apply pressure late game cause you are so darn fast and can recall out if you are about to get caught. Overall, they are better if you only focus on side pushing/applying pressure. I usually go for Symbiotic on easy/ranged matchups where I know I won't have to worry about dueling them.