I have a confession to make, though I have tested at both Ancestry and 23andme, I rarely work on my own DNA matches. Since I tested both my parents at 23andme, and they are on both Gedmatch and FTDNA, I work on their matches and not my own.
Since I manage several kits, I do work on the larger matches for my cousins that I have tested, and I do identify the family connections on closer matches in AncestryDNA, though without triangulation it is useless unless the kit is on Gedmatch. And since I have been doing this for a while now, I don't look at matches smaller than 30 cM unless it is pertinent to a triangulation, or it is my Great Aunt who has no larger matches to work on. (The majority of her matches are going to the 17th century when identified).
I just mentioned why I think I have only one community on Ancestry's genetic communities, so I thought I would compare the differences in my largest matches across the four websites (Ancestry, 23andme, Gedmatch and FTDNA, I am on myheritage and DNAland but both are duplicates of other sites).
On AncestryDNA, my closest match is my daughter followed by my father's sister. In the first cousin section I have two of my father's paternal first cousins and my maternal great Aunt. In the second cousin section I have another of my father's paternal first cousins, a second cousin from the same paternal line, and my maternal grandfather's first cousin. In the third cousin section I have 10 matches, one is from my maternal side, and the rest are all paternal, mainly from my father's paternal side.
Ancestry lists my largest 4th cousin match at 84 cM and it is from my father's maternal line. The smallest is listed at 20 cM in the 4th cousin section. According to Ancestry I have 877 4th cousins or closer, 18 of which are third cousin or closer. I know I have more maternal matches in the 4th cousin range, but I have not looked at everyone who has a tree, and that is probably no more than 30 percent of the matches, but of my 55 DNA circles, only 6 are from my maternal side.
On Gedmatch my first three matches are my daughter and my parents, followed by my Dad's sister, my maternal great Aunt, my maternal first cousin, my maternal grandfather's first cousin, a paternal double 3rd cousin, and my mother's half first cousin.
Between 50-116 cM I have 13 matches, only one is a maternal match. The largest 116 cM is listed as 84 cM on Ancestry. Between 30-50 cM I have 83 matches, I haven't identified them all but what I have is about 30-40 percent maternal.
So on Gedmatch, I share more maternal matches than on Ancestry. What about 23andme? It's a bit harder, my matches there are by percent, but I know 1 percent is 74 cM so 0.5 percent should be around 37 cM.
Through 1 percent I have the following identified matches in order, my parents, my maternal first cousin, a paternal double cousin I haven't contacted, a paternal double 3rd cousin, my mother's half first cousin, a maternal second cousin once removed, another paternal double cousin (sister to first unidentified), and two paternal 2nd cousins 1 removed.
From 0.5-1 percent I have 59 matches. Close to 1/3 are anonymous, and it's close to 50/50 on what I have identified. From 0.25-0.5 percent I have 850 matches, most I haven't even examined. a 0.25 percent match is roughly 19 cM in length.
I used my 23andme kit to transfer to FTDNA with the new availability to transfer the later version of the chip. I don't have all that many matches on there yet, though I know my older kits matches grew with time. In total I have 764 matches at ftdna, 400 identified as paternal and 241 as maternal according to their browser. A lot of the matches here seem to be smaller than I would normally look at so I am not going to analyze the matches.