I recently was tested on the 23andMe site. A secondary goal is to look at families that share my Y DNA haplogroup, R1b1b2a1a1d. One part of this is to compare the results, base by base.
I compared my Y to a couple of others of the same haplogroup, and found a lot (40 – 60) differences on individual bases. Below is a note I sent to 23andMe and their response;
Request #293432” — ” or ” I ” in raw data phenotypes