Magic Launcher doesn't check for ID conflict
Personaly I prefer Magic Launcher because i can turn off the mods i don't want to use with a single click on the ticks. It also loads faster.
I wish it would let me edit the Block ID's from the mods though. I don't have to wait for them to update the mods and the client doesn't have to check if they are up to date witch makes it way faster.
Anyway Magic Launcher FTW.
I run most of the mods in the technic pack with Magic Launcher (There are some I don't like).