Lincoln3457
A Walrus
Modern Armor and Marines / Navy Seals they dominate in the modern world. I usualy discover them around 1880 AD. Modern Armor Around 1935 AD 

Longbows - the do-it-all units of their time.
1) Crossbows require iron, making them impossible in some games - longbows are always there. 2) crossbows cost more. 3) crossbows have a bonus against melee units - longbows have a bonus against *everything* - just in a certain situation.
Crossbows are great units, but they're more situational than longbows. The cheaper longbows ,which can have their strengths (hills/cities) leveraged against any units from macemen to knights, require no resources - whereas crossbows only excel against melee and actually blow goats against anything but. I vastly prefer longbows as a general purpose units for the reasons listed above.
Not to say crossbows aren't *great* units, but... They are more targeted use units (cost more, require iron, bonuses solely VS melee), whereas longbows work VS anything (cost less, no resources, bonuses work VS anything based on terrain).
Well, as I said, crossbows are a *great* units, and I entirely agree that archery units are great fun (and incredibly underrated by this community in my eyes!). I'd happily make do with crossbows if the situation came where I had them and not feudalism, and leave-off on the longbows until later.
One thing to keep in mind about longbows is that their bonus isn't only city based - it's 25% hill based. So, they can get a bit of a stack effect against units in the field too - a forested hill is all you need to make a stack they're in impervious in your timeframe, and even just a regular hill does very well. That gives them a very significant portion of an average landscape they can leverage into significant bonuses against any units. I've waged my fair of effective assaults with no resources and nothing but lonbows and cats/trebs...
Concerning crossbows, the things about them that give me the nod towards lonbows are the resource and horse archers/knights. Once knights come, crossbows are pretty much hooped - longbows are still viable with forested hills on the field, and inside of cities on D - or even on regular hills if you're comparing hammers rather than 1v1 win ratios. Crossbows are at best even VS horse archers, let alone knights. But then again, if you have crossbows, you can get pikes/spears, so that changes the equation - but that's an if...
I find longbows rock any situation. Crossbows - well, you need iron, and then you need to hope the opponent isn't one of those guys that loves to spam horse units (the Mongols, Justinian, or Saladin for instance). I just love my do-everything longbows![]()