These two add-ons are reckoned to be better than the others available. I don't know, not having played the others, but I found Point Lookout to be excellent value. New types of NPCs, new weapons, a great land/seascape, plenty of swimming, and good quests. Not to mention an all-time-great glitch (clue: check out Haley's Hardware) and a genuinely funny psychotropic plant experience.
As for Broken Steel, it's okay, but, with the wonderful exception of Liberty Prime, ultimately sub-standard to the main game. The quests kind of fizzle out, and personally I find Elder Lyons to be the most irritating computer generated character of all time.
If you are not quite ready for Fallout:New Vegas, these add-ons are a very adequate stop gap solution.