Unfortunately Long Bow also means you can't bring a slotted sidearm, and that you will be at a serious disadvantage in archer duels due to the speed.
Long Bow (vs Strong Bow):
Pros:
Straighter arrow trajectory
~10% more damage against peasants, ~50% more damage against armored (rough guesswork based on melee calculator)
Cons:
Fires significantly slower, which hurts most when fighting other archers, kiting melee or defending against cav
Takes 2 slots, meaning you lose out on either a third bag of arrows or a 1-slot sidearm
Can't be used on horseback - not an issue for a foot archer, but makes you less flexible in later generations if you want to MW it
It comes down to your play style. If you want to stand in the back and plink arrows artillery style all day, go long bow. If you want flexibility and to be a bit closer to the action, go strong bow. Also, I'd think long and hard before I loomed a long bow since it is so inflexible.
Honestly, if you can't decide, build your archer with 6 PD and buy both, then loom the one you like most. You'll be swimming in money as a foot archer anyway.
