Welcome  
  
yes a TT is generally better than a T - neither will be cheap - if you can afford to do a single turbo it's probably a good idea to save a couple more grand and do a TT  
  
generally a TT will have less turbo lag for the same power turbo, as each of the 2 turbos can be smaller.. 
  
depends how much power you want to get, and what youre prepared to spend - remember the supercharging option in the mix too..