[Faceman]

The advantages are weapons only evil aligned chars can use. The disadvantages are weapon restrictions for goodies. You'll miss some NPC quests but only if you don't take them into your party and gain hilarious NPC quests for Korgan, Edwin plus the Viconia romance!
Playing evil IMO is not that much different from playing good unlike most people think.
There are some quests that can be done to an evil end or with evil actions during the quest (Planar Sphere, Druid Grove, Underdark,...).
Other - so considered - goody quests are no problem for me either. I just snap at the quest relevant people in every dialogue and make it very clear that it's just about the money for me. Keeping you Reputation low (to maintain party balance) is no problem. Kill an innocent! (But be sure there aren't others watching as it will result in a massacre which drops your rep to an extent where you get kicked out of town.
Apart from party balance however there is no bigger point in lowering your rep. Being evil means double if you have a good rep although you have pickpocketed the whole town and killed some innocent children.
So try it the evil way. You'll get a nice Two-Handed and incredibly powerful Leather armor and some nasty quests and miss out on Carsomyr some minor equipment and Keldorn's/Mazzy's/Cernd's "let's run around twon 20 times" quests.