The smaller base is probably for chandeliers and vanity lighting. Personally I wouldn't bother buying CFLs these days unless they are cheaper and you just need to fill a socket with a bulb... any bulb. I still have over a dozen incan bulbs bought 15-20 years ago when you could get a 4 pack of bulbs for about $1 even 100W bulbs were that cheap and I took all the incans out of everything in the house except for one outdoor light that I rarely use for more than 5 minutes at a time and a CFL in cold weather wouldn't work well in that situation. When I move out of this rental the incan bulbs will go back into all the sockets and my CFLs will come with me to the next place most likely.
One thing I have been looking at is LED tubes to replace 4 foot shop lights that I have as the garage isn't heated in the winter the tubes don't warm up well for about half an hour. The thing that is stopping me is about $10 a tube I figure I will just wait till I run out of fluorescent tubes for the light fixture I picked up 4 used ones at a Habitat for Humanity for $1 each about 10 years ago as they were about $6 or so in the stores at the time.
One thing I have been looking at is LED tubes to replace 4 foot shop lights that I have as the garage isn't heated in the winter the tubes don't warm up well for about half an hour. The thing that is stopping me is about $10 a tube I figure I will just wait till I run out of fluorescent tubes for the light fixture I picked up 4 used ones at a Habitat for Humanity for $1 each about 10 years ago as they were about $6 or so in the stores at the time.