Quote from: Kogs on March 29, 2018, 05:06:09 AM

And if it can only be one of them someone need to chose which one.

For bitcoin and most POW coins, the winning chain is the one with the most cumulative proof of work done.
So the chain that will be orphaned will be the one with less proof of work done.

Quote

And if the decision was made which one is valid, that mean that ALL transactions from this side of the fork need to be valid and ALL transactions from the other side of the fork need to be invalid. And now we are back at the reorg.

You cannot chose some transactions from fork 1 and some from fork 2.

The blockchain doesn't usually split for long enough before a reorg, unless there's a serious problem with node clients or internet partition.
Blockchain.info's Orphaned Blocks page shows that reorgs don't usually exceed 2 blocks
Till date, I think the 2010 Overflow bug is the longest reorg. And that was because of a bug in the node client.