I've used both platforms for VMware infrastructure, if you ask me, I wouldn't touch HNAS in a near future for VMware using NFS.
HNAS is in fact a good product, feature and spec look good, but it's optimized for different king of workload, more on throughput rather than latency.
The company I worked for migrated from NetApp to HNAS and it turned out to be a disaster. We had TEST/DEV environment on NetApp using single SATA shelf. The same workload after moving to HNAS requires 90 SAS disks to handle and still has twice the latency, and still close to useless. 2 years later they decided to move all the workload to backend HDS FC SAN from HNAS because even with HDS's help, the problem could not be resolved. If my memory still works, the HNAS model I had was 3090 and with hundreds 15K SAS disks in the back, the latency is at 100ms over 10Gb.
I manage a lot of NetApp at current job, 6280 is used in our datacenter and I can't be happier. Also don't forget you will loose things like SMVI if you move to HNAS. HDS did provide us with scripts to do things very similar to SMVI that we integrated with Netbackup but you don't get nice GUI from VSC.