Though I am not sure if right comments on, we also insisted PCI-based storage is entirely different.
Rather than a SCSI-connected hard disk drive, PCI Express SSD products often use specialized drivers to communicate using direct memory access (DMA) over the PCI bus. We always think this is game-changing in terms of I/O latency, enabling random read and write performance that's orders of magnitude faster than the quickest storage array.
I also recommend interesting blog from Chad -- VFCache Hello World. You can get more highlights.
There are three reason why putting your redo logs on local flash is not a good idea
1. It is not necessary or beneficial as explained to you here - redo log files have a predictable workload
2. Potential Data loss if you lose your redo logs - what protection would you have for the DAS part of VFCache Split-card
3. Restricted to single instance database only as the redo logs are on DAS
Each instances in an Oracle RAC database need to have access to all the redo logs for consistent recovery.