What is the easiest program to take 2 bluray movies from single BD's to BD-DL's? Just need menu

I have a bunch of blurays that are under 25GB that I want to merge onto a single BR-DL 50GB disc. What is the easiest way to:

Take two a full BD's (with menus and all), and create a simple like "select a movie" screen for that disc.

or

Take two m2ts files, and create a simple like "select a movie" screen for a single BD-DL disc.

I want to retain the quality but consolidate my movie collection into as few discs as possible.