Is the amount of data read/written the same? I'm not clear why wall time is the relevant metric, unless that's the critical driver of failure likelihood. I would have guessed it's not time but bytes.
So for example, a pool with 2 RAID-Z vdevs each containing 5 disks effectively has only 2x the IOPS of a single disk, while a pool with 5 mirror vdevs (i.e. RAID-10) has 10x the IOPS of a single disk.
It's not a big problem if you mostly do sequential I/O but it's a huge difference if/when you do small random reads (e.g. traversing a non-cached directory tree).
In the context of resilvers, currently RAID-Z pools can only be done by traversing the block tree which, due to fragmentation of CoW filesystems, usually leads to a lot of random reads/writes, while a RAID-10 pool can basically resilver a pool while doing almost fully sequential I/O which can be much, much faster.