As for the speed for online surf, no big difference except for the highest one in the Starhub. But our students actually no need for this.
But starhub one get an advertage for us: eg, changing our location or transfering our tract to another guy. Only a little service charge.
If you sign in the singNet, you have to pay a big fee.
Actually for the promotion events, you can check their websites for more details.
Cheers.