jsidhu762: The XP from Flaming Fist mercs isn't much, but good and neutral characters get zero, since they aren't hunted by the Flaming Fist.
Nope, if you are playing normally and doing the optional dungeons as well, you are going to hit the level cap by the time you hit the final chapter. Long term, there is nothing to be gained from having the FF chasing your arse around the Sword Coast.
jsidhu762: You don't need to be evil to recruit the evil characters, but you do need to be evil to keep them.
Nope, you just need to do something stupid (ie, kill a random commoner for no reason) once your rep gets too high or turn into the slayer. The problem here is rep (which is too easy to raise by playing the game normally) and only easy to lose when you're playing stupidly (ie. random killing).
jsidhu762: The tick from Eldoth's poison arrow can shut down casters.
You don't need to be evil to recruit Eldoth and anyone who can use a bow can use arrows of biting. You want to know a smarter way to bring down casters? Bringing your entire party to focus fire on them. Once again, there's no advantage of being "evil" here
jsidhu762: The same goes for Neb's nasty cutter. If you back stab a mage with Neb's dagger and the mage survives the attack, the DoT will chew away at the few hit points he has left. The adventurer's mart doesn't sell a back stab weapon with a similar effect. Remember to give your thief non-detection; NPCs in the game will cast true sight when your cloaked thief is creeping around.
Unless you are playing a solo character, there is absolutely no reason to back stab. If you are tackling a mage (or anyone) who is accompanied by a mob, guess who they are going to target after the thief becomes visible? If the mage is alone, why bother backstabbing in the first place? Overwhelming the caster by bringing your entire party down on them is much more efficient. In BG2, I can't recall a single mage who was a problem to deal with, even Irenicus is a push over. As long as you have a way to bring down their spell protections, most times, they will be dead before the round is over. Once again, no benefits for being "evil" here.
Oh, and if you are dead set on using Neb's Cutter, you don't need to RP evil to get it either.
None of these are advantages when you consider being an asshole in dialog can cut you off from XP and loot. In fact most of the "advantages" you mentioned are still open for "good" parties as long as your rep isn't too high. But it's fine, I already mentioned in order to find advantages for being "evil" in BG, we would have to scrape the bottom of the barrel and that's exactly what we're doing.