Re: T-tail aircraft
Confab has covered most things but I'd also add:-
Advantages:-
Completely clean wings
Cabin noise is lessened- happy SLF!
Also...very minor but greater margin of error for crosswind landings as no low slung pods.
Disadvantages:-
Deep stall (arse down):- In T-tail designs, the turbulent wake of a stalled main wing "blanks" the horizontal stabilizers, rendering the elevators ineffective and preventing the aircraft from recovering from the stall. Stall issues and overotation are also compounded by the fact that in a pitch up attitude it is possible for the wing to also 'blank' clean airflow through into the engines, thus preventing using thrust for recovery and lessening power. I think a 1-11 was lost from this issue.
Also fatigue can be compounded by the 'lever' weight of the epenage and engines over a period of cycles. DC-9/MD-80 family have experienced this I believe.
You pays ya money and you takes your choice!