Here is the short answer,
BLM -
Cons- Too many are around. Too many are complete morons and have completely overcrowded endgame with their idiocy. The job is pretty fun for a while but when you reach 74-75 no one wants you in their parties _at all_, all you have is manaburn. Even though the AF2 isn't the greatest, be ready to go to Dynamis for months only to see every other job get at least one piece of gear per person while you blms fight like wolves when the one piece in a 6 month stretch drops and never again.
Pros- You almost always have a place in every endgame event. It's pretty rewarding to do awesome damage to big monsters. If you don't suck, you will be the mega boss of every ballista match. Mnks, Nins, Wars, and just about every other class will tireslessly bitch you out and try to kill you, but you have spells for every instance and should never die if you use your spells/abilities/mp right. Just watch out for smart Whms.
BRD -
Cons- You will never be able to play another job again. You will be harassed on an hourly basis for merits, general partying (before 75), or to replace RDMs in parties in bibiki bay. PLDs are your worst nightmare. If you thought BLM was boring, boy are you in for a treat with BRD - the only caster in FFXI where every spell sounds exactly the same.
Pros- You will always have a spot in a party. You can literally walk into parties naked and no one will say a word. You are very useful for just about every element and stage of this game. You can get away with telling the party that they are a bunch of fags, leave, and your reputation will not be affected since everyone wants your songs regardless of what kind of asshat you are.
NIN-
Cons- You are spending sooo much gd money. So.much.money. There's no way to reach into other peoples computers and bitch slap them for stacking all of their job abilities at once and weaponskilling at the start of battle (cough drk war mnk.. did I mention drk?).
Pros- You own PLDs in exp, and do pretty well against HNMs too. Highly desired job. You are easily one of the most overpowered jobs in this game. Other stuff that I can't mention cuz I really cannot think of anything (but only because I'm retarded, not because there is anything lacking).
I had fun writing this lol, but don't really take it seriously. I guess it wasn't such a short answer either.
