What are the advantages of all-flash storage over other types of storage?

It has better performance than Hybrid storage and customers can have more IOPS,
for the mission critical application customers better use all-flash arrayas

Speed (IOPs), increased reliability, compactness.

If your application does not needs those you can go with legacy solutions as far as price justifies.

Sooner or later even price will be in favour of all-flash

In general, all-flash arrays have much better price/performance (in case if turning on DECO is not slowing down the array - some vendors have this issue, so PoC is needed) than hdd-only or hybrid arrays. Higher performance, lower power consumption per TB. The support cost for the HDD-only and hybrid arrays will be more an more expensive, as the HDDs share is going lower, and the main R&D is moved to all-flash arrays. Of course, in some cases (i.e. video surveillance, D2D and maybe several others), HDD-only arrays are the better option, so it's better to make a decision case-by-case.

It all depends on the Budget as well....if required High IOPs for Database or other read/write intensive services and also budget is not a issue then go for All Flash...Otherwise combining SSD with NL-SAS alongwith tiering / cache features will suffice purpose in most conditions...

The selection of All-Flash Storage Solutions depends on requirements and the goal any customer is looking to achieve at the end.

All-Flash is not a fit for all requirements......

"If a customer needs a storage solution with high to extreme performance,
Rack-space
efficient, power and cooling efficient (environmentally friendly),
build-in compression; then they should choose All-Flash solutions."

It is not all about the performance that storage manufacturers are very aggressive to sell their All-Flash boxes.

Just think about SAS disks..... those were used as performance and SATA as capacity.

Enterprise SAS disk technology is limited to 1.8TB/disk only; that is why storage manufacturers are promoting their All-Flash to fill the capacity gap created because of SAS disks technology limitations.

The modern Flash disks are covering both requirements (Capacity+Performance) but are still expensive (if we assume the same RAW capacity).

If a customer comes with the requirements that fits to an Enterprise Hybrid Storage solution like 40%SSD, 30%SAS and 30%SATA; 400TB RAW in total, then they should select All-Flash instead, as both solutions will not have any significant cost differences.

If a customer's requirements (Performance+Capacity+Cost-effective) fits to SAS then they should choose a SAS based storage solution.

If a customer needs an archival storage then they should choose SATA based solutions.

If a customer needs a storage solution with high to extreme performance, Rack-space, power and cooling efficient (environmentally friendly), build-in compression, then they should choose All-Flash solutions.

If customer needs less SSDs/Flash disks; like.... 10%SSD+45%SAS+45%SATA, then Hybrid type of storage solutions will be a good and cost-effective option.

All-flash arrays are more costlier than any other storage arrays.
Will give more performance with less latency when compared to any other arrays