Here's a quick breakdown of the distributors with whom I've had experience with, for the OP's reference -
Steam - Massive user base. Low entrance requirements (in the grand scheme of things). You only need to sell to a small portion of this active user base in order to get by financially.
Indiegamestand Store - Reasonable, since their user base is there to buy indie games specifically. So you have a large portion of their user base targeted to your genre. You also get to track how many users want your game on a 'pay what you want' deal, which can be lucrative.
Aldorlea & Amaranthia - Both great affiliates for RM games, since their user bases are there to buy RM games, simply put.
Desura - Honestly, I have mixed feelings about this distributor. In my own experience, users only buy my games if they're discounted very heavily, and even then we're talking less than 10 units. They also have a high minimum payment threshold of $500/£500. I had a lot of trouble publishing Atonement: Scourge of Time on there - they practically ignored me for several weeks until I pulled some strings to show that I wasn't going away. Keep in mind that I already have four games on there at this point.
Greenmangaming - I like this distributor, even if their user base isn't very into RM games. Their marketing managers keep open communications and never ignore my emails (see: Desura), and they're more than happy to arrange promotions and such.
Fireflowergames - I've not sold many units on here at all, even with 80% discounts (which I put on to test the user base - I've never discounted my games that heavily anywhere else).
Shiny Loot - These guys have interesting ideas, but again, not many units sold.
Indie City - Never sold a single unit on there.
Then you have bundles. These can be helpful in getting your product Greenlit for Steam (though there are some drawbacks, which I'll go into in a second). Then once you're ON Steam, there are more bundles that only sell Steam games.
IndieGameStand PWYW - One of the most lucrative deals I've ever done. Try to get booked up for an IGS sale before going into any bundles because your game alone gets the spotlight.
DailyIndieGame - They run both solo and bundle sales.
Groupees - Typical bundle site.
Indie Royale - Typical bundle, however revenue from here goes straight into your Desura account (see: minimum payment threshold). I've had to fight on two occasions to get them to pay out when the bundle didn't bring me above the threshold.
Indie Gala - Typical bundle.
BundleStars - They only deal with games that are pubished on Steam. The most lucrative bundle I've done to date.
Lazyguysbundle - Typical bundle.
Bundles have upsides and downsides. On one hand, using them to acquire the votes you need to get Greenlit will eventually get you onto the Steam platform (as long as your product is marketable). However, you'll have to give Steam keys out to everyone who purchased the bundle, so we could be talking tens of thousands of users on the Steam platform that will ALREADY own your game once it get published on there, taking a significant portion of your interested market out of the equation.
Another downside I have noticed is that people who basically get the game for pennies don't feel invested in the product, and will happily swing by to leave a negative review after say, 10 minutes of play. Basically, you're inviting RM trolls to come and leave a permanent black mark on your store page. On the other hand, you have 'real' customers who will feel invested in their purchase (something that comes with buying indie games, I think) and they're usually more willing to take a balanced approach to writing a review, usually leaning more on the positives.
So, there you have it. I can't discuss figures with you, but hopefully this will give you (and others) an idea of where you can distribute your games. Good luck!