Hello I'm hooked on the 5K 2015 iMac (M395 with 4.0 GHz i7) and really in doubt when it comes to the storage options. My only realistic choices seem to be the 512 GB SSD or 2TB fusion drive. I'll use the machine for editing raw photos (24 MP) in Adobe Lightroom, programming (web development, iOS with Xcode etc) and usual every day stuff. I might go into video or music stuff at some time, but I'm not sure at all. I have a NAS where my entire photos library is stored, but I prefer to have the collections that I'm working on, stored locally. (And synced using Synology Cloudstation) Currently I use a late 2013 15" rMBP with 512 GB SSD. I know that I can always add more external thunderbolt drives if needed, but that's not an elegant solution for me... I read a lot of other threads about the subject and while a lot of people are happy with Fusion, some people talk about performance issues when editing videos etc. http://barefeats.com/imac5k12.html According to this test, it seems like the difference is pretty small except from writing huge amounts of data, and the Fusion drive on 2015 models seems to write almost as fast as the SSD on 2014 iMac and 2013 MP. But honestly, I rarely have to write more than the 4 GB (which Fusion is buffering on SSD) at once. And when I do, the data source will either be the NAS (via 1Gbps LAN) or the SD Card, both of which are WAY slower than the HDD. Anyway, here's my pros/cons. Do you have anything to add? Or can you tell me if some of these points are more important than others? Thanks in advance! 512 GB SSD Pros: Consistent fast performance of all 512 GB of data Only one point of failure (a fusion volume dies if either the SSD or HDD dies) Cons: Pricey: 250$ more than the 2 TB fusion (Denmark prices) I'm already struggling getting enough free space on my 512 GB rMBP, so this might be insufficient I plan to use this machine for a long time (maybe 5 years) and then, 512 GB might be way too little, if I also want to backup my iPhone/iPad. OS and apps grow constantly... Because of that, I might spend another 250$ on an external 2GB Thunderbolt drive to match the 2TB fusion capacity Then I'd have more stuff on my desk, more cables etc. And I'd have to manually manage what data to store on SSD and HDD It just feels SOO STUPID to have an external disk on my table, while wasting the iMac's built in 3.5" HDD slot (but I know that it's not trival to install storage in an iMac) 2 TB fusion Pros: Cheapest option No worries about where to put save which files No need for external drives on my desk Enough space for the next 5 years If I need more SSD space, an external Thunderbolt SSD might be less bulky than an external HDD? Cons: Performance might be unstable Two storage devices to fail.