When comparing WhatSizeMac vs DaisyDisk, the Slant community recommends DaisyDisk for most people. In the question“What are the best disk space analyzers for Mac OS X?” DaisyDisk is ranked 1st while WhatSizeMac is ranked 9th. The most important reason people chose DaisyDisk is:
While working on your Mac you create and download a lot of files, but rarely delete anything. As time goes by you have less and less room for your data. DaisyDisk finds those hidden unused gigabytes.
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Pros
Pro Updates information in real-time
WhatSizeMac is able to listen for file system events and update itself in real time. So it never needs a full volume measure but once in a very while.
Pro Helps find and delete files taking up HDD space
While working on your Mac you create and download a lot of files, but rarely delete anything. As time goes by you have less and less room for your data. DaisyDisk finds those hidden unused gigabytes.
Pro Awesome visualization of files on drive
DaisyDisk gives you a perfect overview of all the disks connected to your Mac, be it Macintosh HD, flash card, Thunderbolt disk or network storage. And does it in a beautiful way.
Cons
Con Poor tech support
No update for Mojave.
Con Commercial
WhatSizeMac cost $29.99 and there is a free trail available.
Con Calculation based on 1000 not 1024
It's nice to have a base 1000 (MB, GB, …) calculation but it should be optional. Default should be 1024 (MiB, GiB, …)