I talked to the dealer today and told him i wanted a 12" and a 18", he said he will try to find them for me. He said for digging up roots and stumps the 12" would be best for it. It won't bother me to have a couple options with buckets though. I'm sure i will put them all to use. Thanks for the great advice. I'm going to research rock teeth now and find out what they are lolThe advantage in having a 12" bucket is in good soil or clay without alot of rocks, this allows a narrow trench and less overall disturbance. Digging in rocky soil or loose soil where the sides readily cave in I prefer a wider bucket since you can cleanout the trench faster.
Recognize that when digging in rocky soil and you hook a rock with the bucket it really doesn't matter whether it is a narrow or wide bucket, either one can provide the same forces to peel it out. The narrow bucket is not really going to dig better in the majority of cases.
What I have now is one 12" bucket with standard teeth and one newly aquired 12" bucket that I will put rock teeth on. I have an 18" standard bucket and is my preferred bucket for most jobs.
I use the 12" bucket to install small water and sprinkler lines in lawns where less ground disturbance is preferred.