The answers are to your questions.
The engines are going to be made visually larger so obviously better performance over all this.The fusalage is wider taller and longer. With this the luggage can fit underneath but only half the aircraft the other half is for fuel. The 757’s will be put out of production due to”a shrinking order book” as a statement made by president mullally of Boeing. The 727-300 would only be temporary i suppose until the 7E7 comes out.
🙁 🙁 what ….pigs dont fly…aawww:(