Why does one tx go trough and the other not?

[vit1988]

A smart guy fools a gambling site (which accepts unconfirmed deposits but allows withdraws only after all deposits are confirmed) by depositing bitcoin in low priority transactions (unconfirmed inputs, no fees). When he doubles his wage he waits a day until his low priority deposit is finaly confirmed and cashes out. When he loses his wage he somehow achieves that his deposit do not confirm at all and just creates a new account.

What I don't understand is why one tx gets confirmed and the other one does not. Does not look like a double spend to me but maybe I'm misinterpret blockchain data.

Here are two example transactions:

Confirmed tx (and I have no idea why this one went trough but the other did not):
https://blockchain.info/tx/3c2ac5ce691d99770c654f4fa2a69b1825e93158fedc3436de07f18bb6f91bf4

Unconfirmed tx (and I'm pretty sure it won't confirm):
https://blockchain.info/tx/1f006d66ea95ce46cafe4be66c149d7299fd35d4aa7287e5db4f435dce66eda1

[apxu]

What I don't understand is why one tx gets confirmed and the other one does not. Does not look like a double spend to me but maybe I'm misinterpret blockchain data.

Let us take 2BTC and split it to 10 outputs.
OK. Transaction is confirmed. Now we have 10 utxos  with 0.2 each
Can we merge our 10 utxos into one today without fee? No. Miners will threat this transaction as low-priority
Can we merge our 10 utxos into one tomorrow without fee? Yes. Miners will threat this transaction as high-priority

BTW, what site allows to gamble unconfirmed deposit? 

[vit1988]

Ok. But both of those shown transactions have the same "unconfirmed input, no fee, low priority" pattern, still one gets confirmed the other does not. Why that?

Site is https://satoshi-karoshi.com - instant deposit & play but as said withdraw only after all deposits are confirmed. Worked fine for over a year now