Not exactly. The rewards per block are the same, yes (or we can chalk it up as being the same) but in reality they vary a little based on transaction fees for whatever transactions were in that block. It averages out though so let’s just say they’re the same per block.
With that said, your theory would hold true if each pool gets assigned the exact number of blocks to mint. This is not the case however. The number of blocks a pool gets to mint is directly proportional to the total amount of stake that pool has delegated to it albeit with some variation. There is also the question of saturation and pledge. I’ll get to those in a second.
So to close on the previous point, a pool gets assigned more blocks to mint the more stake it has delegated to it in total (including its own pledge). This is not a 1-1 match though, it just increases the probability a pool gets to mint more blocks so it will vary per Epoch a little bit which in some cases, might actually favor slightly smaller pools (pool with less delegation) because if they’re lucky, they get a few extra blocks to mint and your return on that is higher. It does average out though with time so take that with a grain of salt. The gist of this, is that over a longer period of time, you’ll see similar rewards regardless as long as the pools operate well. You’ll either see a higher return but less frequently (smaller pools), or a smaller return more frequently (larger pools).
The other thing to consider is that pools can hit a saturation cap with total delegated amount. That cap is fairly high now, but as we have so many pools, the parameter that controls what that cap is will likely change soon and as a result, people delegating to top top pools will saturate faster and rewards will diminish. i.e., the probability of a pool minting a block does not increase after a certain point and so the total number of blocks don’t go up with delegation after the saturation point, and so more delegates at that point = bad i.e., fewer rewards per ADA staked.
Again, the saturation point is still pretty high now (don’t recall what it is off the top of my head) but you can get estimates form the IOHK shelley rewards calculator.
And of course the number of blocks minted and thus rewards depends on the pool’s performance (is it up and healthy when it’s supposed to be) otherwise it will lose on the chance to mint blocks.
As far as pledge is concerned, I’ve explained this in detail in another post so I’ll just summarize here real quick. A pool pledge ensures pools have skin in the game to prevent attacks on the network. But it also helps with rewards. Technically the pool pledge CAN have a significant role on the rewards a pool and its delegators get however this is controlled by a protocol parameter, which is currently set to such a low value that pledge doesn’t really make much of a difference… it’s so insignificant all other factors will be more important right now, unless the pledge is too low (like < 10K maybe, or too high > 10Million) then you can think of the pledge as really not that big of a deal. It still counts, and shows you a pool operator’s intent, and may play a bigger role sometime in the future, just not right now.
Finally, 2 notes on ranking and network. I think it’s a good idea for decentralization and stability of the network to support the smaller pools now. Yes, you may miss on a tiny bit of rewards, but it keeps pool operators engaged and helps the eco-system and you’ll eventually recoup those rewards (I hope) assuming the probabilities pan out slightly to the advantage of smaller pools. Also, you de-risk getting on a pool that will ultimately hit saturation limits and losing on rewards because of that. All in all, it’s your choice. I would certainly appreciate support for CPX 
Ranking in Daedalus right now is “somewhat” random. There is a method to the madness but it’s more or less madness right now, and will be for a few weeks/months, until the networks rewards and pool performance truly show up and dominate the scoring criteria. Right now, it’s just meh… so don’t be concerned by staking to a pool that is “red” in daedalus… if you monitor it long enough you’ll see those “red” pools come up in the top 10 and the top 10 in the low end and so on and so forth. This only holds true now and the near future though until you can see how pools actually are performing and holding up their end of the bargain. It will take a few weeks/month for that to settle down though.
