All of them.
Is a good practice to choose wisely your peers with who you have channels. always study their peers too and with who they have also channels.
That way you can have a map of your possible routes.
Usually wallet apps "learn" the previous payments paths and try to take the same if were successful. Is named mission control.
But not always the previous path will repeat OK. So you will have the option to reset the mission control and switch between bidirectional or apriori path finding. But use this only in rare cases when you do not have another option.
Some wallet apps let you also to choose the first hops / channels through which you want to make the payment. That could help sometimes with a faster payment.

Failing and trying different payment paths

Caused by dumb node runners not hiking fees or lowering Max HTLC on dried-out channels.

As a permission-less network people don't need permission to do stupid things

• Running mobile nodes for example, the intermittent connectivity means incomplete graph sync and slow startups / push-awake services cause inbound failures
• Tor/Onion Messages, high latency and failure probability at the network layer
• Too many channels, even people that run highly available nodes have a tendency to have channels they don't need thus bloating the graph with bad data
• Suboptimal channels, few people optimize their channels for performance... If you're in NYC you probably don't want your first hop to be in Singapore

Granted people generally don't know this stuff and there's a lot of bad tools out there that send people down these paths, we're trying to fix that with ShockWallet and Lightning.Pub