Oh noes! A highly unrigorous look at essentially incomparable numbers.
Meme of the day: Find your stories on an archive that does hit counting. Look at the top 10 and observe any patterns. 
firefly124 did this and I found the exercise interesting, though the patterns I noticed are different from hers because my writing habits are quite different. I'm essentially mono-fannish, for instance. Anyway, here are my AO3 & FF.net top tens.
| title | ao3 hits | ao3 comments | kudos | bookmarks | ff.net hits | favs | reviews | wordcount | notes |
|---|---|---|---|---|---|---|---|---|---|
| Dust on his hands from the sky | 269 | 1 | 1 | 4 | 7640 | 33 | 13 | 25161 | Giles/Xander |
| The Wight | 258 | 0 | 7 | 7 | 612 | 15 | 2 | 15127 | Giles/Xander |
| Dreams & Memory (Art of Fugue mix) | 229 | 5 | 1 | 0 | n/a | n/a | n/a | 2094 | gen, Dr Who, Remix 2010 |
| Breaking Glass | 224 | 0 | 2 | 0 | n/a | n/a | n/a | 9817 | Giles/Ethan |
| Arms and the Man | 219 | 1 | 13 | 6 | 7154 | 22 | 16 | 47998 | Giles/Buffy |
| Professor G's Uncanny Scoobies #1 | 165 | 1 | 7 | 2 | 954 | 21 | 3 | 11853 | Giles/Xander |
| The Santa Ana Winds | 161 | 0 | 0 | 0 | n/a | n/a | n/a | 2424 | Giles/Buffy |
| Helios Hyperion | 149 | 0 | 2 | 0 | 4240 | 14 | 7 | 4121 | Giles/Buffy |
| Sparks | 143 | 0 | 0 | 0 | 1253 | 15 | 3 | 4250 | Giles/Xander |
| Thusia | 136 | 0 | 1 | 1 | n/a | n/a | n/a | 20246 | Giles/Buffy |
"The Santa Ana Winds" is up on FF.net but it's part of the Helios Hyperion series so its hits are counted there instead. Some stories, like “Thusia”, I chose not to put up on FF.net for content reasons. Others, like the Dr Who remix, I just forgot to put up there. FF.net has very different reading tastes, however. For contrast, the FF.net top 10:
- Dust on his hands from the sky (7644 hits)
- Arms and the Man
- The Adventure of the Displaced Watcher
- Legacies
- Breathing
- Helios Hyperion
- The Elevator Problem
- Cloud Animals
- Reconnection
- Watcher’s Child (3071 hits)
Top ten from my own fic archive:
- Blackmail (kinky BG) (1858)
- Four Nights and a Revelation (Core 4) (1717)
- Liegeman (aka Blackmail part 3) (1711)
- Tradition & Protocol (angsty BG) (1553)
- Dust on his hands from the sky (1501)
- Please (unfinished T&P short) (1330)
- Polestar (aka Blackmail part 2) (1277)
- Giles Makes Good (Core 4 story G/X followup) (1246)
- Breathing (romantic BG) (1201)
- Apples, Oranges, and Pears (GX) (1183)
Conclusions:
- I am an obscure & unread fanfic writer.
- Nobody is reading on AO3. FF.net has an order of magnitude more traffic. Hell, my static website has more traffic.
- Remix can get an obscure 2nd Doctor gen story some readers, but it can't get a Buffyverse remix readers (that was one of my least-read stories).
- FF.net readers are as averse to comments as AO3 readers. They seem slightly more likely to favorite, aka leave kudos.
- AO3 reads more slash.
- FF.net & my archive readers prefer Giles/Buffy.
- Everybody likes Giles/Xander angst.
- I should post more stuff on AO3 just because it's a stable archive, even though nobody is reading. Such as "The Elevator Problem" and the kinky Giles/Buffy.
he said you can go sleep at home tonight / if you can get up and walk away
tell me, who are you? / cause I really wanna know
That really depends on the fandom. For some reason Buffyverse gets absolutely no hits there, whereas smaller fandoms get loads of hits (and kudos). I get more hits on my really bad X-Files fic on AO3 than I get on my new Buffy fic (and I get at least one kudos or comments to a The Mentalist fic on AO3 pretty much every day).
I've also gotten the impression that AO3 isn't for reading (?!?) but simply for safe archiving.