Niles: I drove a 40 foot Bluebird for years and have recently moved on up to a Liberty 45. My personal experiences is that there is very little difference in mileage, manaoverbility and parking between the two lenghts. My perspective on size is bigger the better. You never have enough storage while traveling, if you plan to live in it a while the extra space is worth the trade offs that have been mentioned by others.
Ideally, you dont want to buy a few coaches to get what you want. The cost of buying and selling, taxes and fixing items you will break in learning how to operate the coach is expensive. Do your homework, fine a coach you love, then look at others to insure its the right one. All coaches have a heart and soul. If a previous owner loved her, took care of her and treated her well, in all probablity the coach will serve you well. However, buyer beware, if your prespective coach was rode hard, abused and neglected you will be in for a real heart ache. There are to many complicated mechanical items that you dont want to be replaceing.
I also always say, pray over it, He wont misguide you!
Matt