i think its not a good idea to just focus on one platform but if you think there is potential just for developing on one platform just make for one of them and after it started giving you benefits, start working for other platforms.

for puzzle 2d indie games, i believe its more popular on mobile platforms like android and ios. so if you are very comfortable working for mobile platforms, its better to start you game for them but working for pc is much simpler. you can test and debug you game so fast. all controlls can be simply defined but mobile is a little harder because you have to debug it on a real device to be sure controlls work very well. so if you are not exprienced enough just start working for pc, when you built you game its just about changing controlls to move it to other platforms(for engine like unity its a simple process, if you write a good modular code it will be simple too but if you make you code unmanaged and write spagetti code it will be hard)

as i know googleplay has no policy so every program and game you put on there will be accepted, but greenlight has some filters that makes it a little hard. i think both them take 30percent of every sale.

From a sales standpoint, both. You can't afford not to do both.

From a beginner's standpoint, Google Play is probably the easiest to get into. Might get low sales though, but at least you get on the shop fairly easily.

I think you hit on one point.

It is a concern that many companies --- including giant products like Microsoft's Windows 8 --- have done badly.

PC games should have a different feel and approach than a mobile game. Both of these should have a different feel than a console game.

However, it is also a mistake to ignore commonalities. You can develop software where 80%, 90%, 95%, maybe even more, is shared in common between platforms. Of course there are some differences, changes between UI is one difference. But there is also much that says the same.

When the additional cost to target over a billion additional devices is so tiny, it is often foolish not to take advantage of it.

What answers do you expect?

Your describtion of your game is still quite vague (Better than what you sometimes get on this forums though), we don't know what you want to get out of the game (maximum amount of money? Maximum amount of coverage to promote your Indie team?), you propose wildly differing revenue models (Ads vs. Paid Premium game) while still having decided on one, and you seem to expect some answer most probably no-one on this forums can give you just like that.

Now, what YOU can do:

1) Market research:

- look into revenue numbers for similar games on both platforms, both for paid and ingame ad models. See what you could expect for your game on each platform. These numbers are hard to come by, but sometimes they get published. Maybe somebody around these forums has a link, maybe you need to consult google.

- look into the process and cost of getting unto each platform. Make sure you do the FULL rundown. Its not only getting enough fans to get greenlit (and be careful about straight off buying them, it seems Valve wised up to the bribery some greenlit games where using to get greenlit), or paying some fees to be able to upload your game to the store.

There are unique costs for each platform that you need to be aware of. Testing on Android can drive you nuts from what I hear from Android devs, you either shell out a lot of money for different android devices and the time to test your game on all of them, or you risk getting a bad rep because the game fails on multiple devices. Theoretically also a problem with Windows, but I hear less complaints about that, so I guess compatibility is better by now.

- Try to get a rundown on how big your potential market is on each platform.... that is of course a tough nut to crack, but you could for example look at the amount of similar puzzle games than yours, and see how they are doing revenue wise.

2) Really look into how much effort it is to create a build for both target platforms.

- Depending on your game, that might not be too hard. Most important things to change is control scheme, then making sure graphics and screen resolution / aspect ratio is correct for each platform, then comes all the rest. Maybe concentrate on the two most important points I made and see how your game holds up on each platform. If you are lucky, gameplaywise it will do just fine.

- This is of course much easier if you use an Engine like Unity or Unreal Engine 4. There building for different targets is just some clicks away. Of course that will not handle differences in control schemes, Graphics and all that, so you still need to do some tweaking...

My personal opinion:

1) be careful with your expectations on mobile app stores. To make a fortune there, you need incredible luck (a very good game, exceptional marketing, and still some luck)....

To get any meaningful revenue with ads, your game must be downloaded AND played A LOT! Worked fine for Flappy Bird, but how many other have seen similar numbers? I guess you can count them on one hand.

Mobile App stores are flooded with hundreds of new games every day, and revenue margins are extremly low, so either you are one of the top few % and make good money, or you are not really making any money at all...

So if you are going mobile, I would really think long and hard about revenue model (premium games are a hard sell and still make not much money (if you are not a known studio and can charge 5$ for your game), but a F2P model with inapp purchases might give you a better chance at making a meaningful amount of money)... and I would really try to bring to PC, where game prices haven't been raced to the bottom this much yet, at the same time.

2) Getting greenlit (without cheating ) takes time and money, you need to build a community BEFORE you can even launch your game. Same as with Kickstarter. So you will need to have somebody dedicate quite some time to that, and set aside some time and money to create your marketing materials and campaign.

.... not that you wouldn't have to do that anyway for mobile, as your launch might be a complete waste without a lot of pre-release marketing (your game will fade quickly into obscurity)