Are the existing window frames in good shape? Tear out involves new inside/outside trim etc why do that if your windows are basically sound.

For our remodel we replaced, you can't tell the difference. To cut costs, the windows on the side of the house are vinyl in and out, a sound but less expensive type than the interior wood framed. We also changed the style of some at no extra charge. If it is important to you, make sure that you get your contractor to finish the interior with window sills, I was surprised that I was going to loose my sills with the replacement windows and had to ask for them with the new windows. We lived in our project as well, the window work was quick.

I plan to do a tear out, but that is because the person who last remodeled my house didn't change the window sizes and they are all tiny. The house is on a lake and you can barely see it from any room in the house. More and bigger windows are required.