So I used this before as a run, to see which main fraction gave the most EXP. But of course, if you play it vanilla style, you can only pick one or do a certain of number of quests before one fraction gets jealous and cuts its ties with you. But with this, you can have your cake and eat it too. Just a warning, before continuing your game, MAKE SURE YOU SAVE BEFORE DOING OH MY PAPA. So that way after you are done with DLCs, you can do seperate saves and do each fraction in each.

IMO, I saw Yes Man gave the most EXP, with me ranging to level 37 with almost all Skills to 100.

http://www.gamefaqs.com/boards/959557-fallout-new-vegas/60786708