757 is the best of these options, assuming they are all domestic configurations. The 757 has the most leg room, and it also is a separate cabin.... if they bring the jet bridge to the correct door, coach will turn right to board and first will turn left, meaning that the flight attendants can quickly serve pre departure drinks and its calm and peaceful in first during the boarding process.

The 767 domestic is VERY tight and many people have complained about the first class on here.

The 737 is OK, but not great, and its not a private walled off cabin like the 757.