If all goes according to plan, then yes, all you get by renting a huge farm is a larger portion of those 24 coins in each block.
However, if you're the first one to do so (instamining the earliest blocks), your percentage payout on those earlier coins will be greater than if you rent the same large amount of hashrate later once more miners jump on the coin. Like, let's say Metalcoin has 6 gh/s right out of the gate, and you rent 3 gh/s-- this will give you 33% of all Metalcoin mined for the duration of your rental. But if you wait until the hashrate grows to 27gh/s and then rent 3 gh/s, at that point you're spending the same on your rental but only getting 10% of all Metalcoin.
There are other advantages of renting large hashrate early. Sometimes a new coin's block release timing will have an error, and a large amount of hashrate will find blocks more quickly than every 2 minutes as per target, kind of like overdriving the release time. This is an outside chance situation and usually is detrimental to the overall perception of the coin, since it relies on an obvious error in the code which shuts out the support of other crucial early adopter miners, but I've seen it work quite a few times.
Renting large hashrate is most effective on coin releases with short PoW and high block rewards as a percentage of total supply. The most recent example of this is Utilitycoin. It's less effective on PoW-only coins but this adds more overall stability through better distribution.
Perfect explanation.
And thats why everyone wants to be the first... and some pools have dedicated machines only for compiling wallets as fast as they can :-D
So *that's* why you've always got the first pool up! A dedicated wallet-compiling box! Shoulda known