1. Even though the games share a comomon title and lore, they play as two totally separate games. If you start in EQ1, you'll find that there are few players at your level range. Most of the player base is entrenched in the top tier raids.
You will also be disappointed if you spend time on the old graphic engine of EQ1, then come into the light and see the amazing graphics of EQ2.
2. EQ2 is generally a mature crowd. I can't remember tha last time I saw and OMFGLOLOorZ11!!ONE! in chat. There will sometimes be a flare up by some tool, but he is quickly ignored. Folks are friendly, funny, and willing to help out.
3. EQ2 is easier than FFXI, and you could grind your way to level 70 in 2 months or less. Of course that would mean missing all the content, lore, quests, and other special facets of the game. I have been playing since the game launched in November 2004, and have only just recently reached level 69. I play casually, do quests, tried crafting (didn't stick), and mentor my guildmates. That's the satisfaction I get from the game, and that may not be what others want.
4. See #3.