I'm booking a flight from Las Vegas to Los Angeles, I'm coming from UK before so have opted for First class to allow for baggage.

The price of each airline varies by around $20 leaving me open to suggestions as to the best airline to go with.

American, Delta or United ?

The key things I'm looking for comparables on are:

Priority Checkin
Fast Lane Security
Priority Boarding
Lounge Access
Comfort

I thought this would be better suited in the Las Vegas thread, hopefully those with knowledge of the airport could give some insight to use of priority lanes and their usefulness or not

Thanks in Advance