they are both lovely fish if you have the room....just depends on what you like....a koi is a koi---even though the die hard koi kichi don't consider butterfly to be a true koi....and depending on what your looking for pond quality or better....most butterfly have very poor patterns....but, so do pond quality short fins....
Lawanna

There are a few things about longfin that most Koi breeders wont tell you. They are hardier and less prone to the ailment of standard Koi. All of my fish are longfins. Elegant and tuff. They dont have the solid color patterns all the time but some do, I have a beautiful 26" shank a shushui that is stunning. So if its longfins you want do it. Beware of half breeds. When buying young fish the fins need to be verrrrry long, looking much out of size to the body. hope this helps.

Thanks, aquawise. Can you suggest a place to get them? I don't mind if they're small (I'd rather find inexpensive small fish than expensive large). I'm looking for about 6.

some times on ebay you can get them in lots, as small fish? I just got pond grades from the local pet stores.

You can try http://www.classykoiponds.com they have tons of small butterflys.. 35$ on up.. not sure if they ship though.. you might call and ask.. I have gotten all my koi from there..