ATTN: M1 owners using Xcode - Mac mini M1 with only 8GB Unified memory

Get the 16 GB option. Compilation and linking are resource-intensive, and many developers also tend not to be all that patient.

Computers are a hierarchy of speeds and bandwidth, and a balance and trade-offs among the storage tiers.

The processor is fastest (but processor storage is also most expensive and is smallest), the processor cache fast, main memory less fast, main storage on an SSD on a fast connection very speedy, main storage on an SSD on a less-speedy interconnect less speedy, out to hard disk storage (big, cheap, slow) or remote storage slowest.

Interestingly, it can be faster to fetch data from a remote server than fetching from the slower sorts of local storage.

Now…

Trying to map performance and a memory capacity comparison across a different system design can be precarious.

Lots of main memory (RAM) is great when external storage is slower, as you can cache the data from the slow storage in the faster (RAM) storage.

But if your main storage is faster, you need less of it and can use main SSD cheaper storage, as you’re not waiting as much for main SSD storage.

Conversely, if your main storage is a hard disk, you want lots of memory (RAM) to try to mask the (lack of) performance of your storage.

Apple M1 moves the memory closer and faster, and with a very fast SSD connection. Which makes the cache and main memory and main storage trade-offs a little different from those of a computer based on an Intel processor design.

Get 16 GB. Get more storage than you might think you need too, if you plan to keep this for (say) five to seven years. Neither of these can be upgraded. And ~nothing with macOS or Xcode or apps is getting smaller.

I have an M1 Mac mini with 16GB (max memory option) and a 1TB SSD. It is blazing fast. Faster than any Mac I've touched including the iMac Pro and runs Xcode like quicksilver. Perhaps only the Mac Pro 2019 is slightly faster at only certain specific tasks.

It's unlikely you need more than 16GB of RAM. Adding RAM doesn't necessarily improve performance so much as it gives you more room to run more things at once or work on larger files. Looking at Activity Monitor and Memory you want to watch your memory pressure. If your pressure is high you need more memory. If you are pushing 32GB hard with a high memory pressure 16GB is likely not enough. But if your memory pressure stays low with 32GB it might be overkill for your needs. Keep in mind that macOS will use a disk cache in RAM but will free that RAM up as Apps and the OS requires. The system will swap as necessary and swapping to SSD is a lot faster than swapping to an HDD. I would choose the 16GB RAM option over the 8GB RAM option. I am finding it very difficult to bring the M1 to it's knees, it just devours everything I throw at it.

if you can wait a bit, the M1X should arrive soon and the M2 next year. They should improve considerably over the entry level M1 which is already making the industry sweat and freak out. Intel is looking at RISC V, Nvidia wants to buy ARM Holdings, Samsung is partnering with Microsoft on a new ARM for Surface. AMD is dusting off an old ARM project and rebooting it with potential redesign. Apple proved the tech with a 300% efficiency improvement. This is a big deal, it's going to be as disruptive as the iPhone was. The only difference is the manufacturers are not making the same mistake the cellular industry did when the iPhone first launched. Apple has a lot of room for improvement, the future is wide open. For the last decade plus, Intel has been making only marginal improvements to x86_64 but its days are numbered.