It has been pointed out, but the actual write speed is around 256 MB/sec, not 220. A 7200 RPM hard disk may do 123MB/sec in sustained write in some benchmark, but given it has huge seek time and latency compared to any SSD, it's performance is far lower than the M4 in normal workloads that don't involve writing gigabytes at a time. Typical best performance with 7200 RPM Hitachi and Seagate drives in MBP is more like 40-50 MB/sec according to iStat in my experience.
Also in typical use the split between read and write on a desktop or laptop is something like 95% read and 5% write. Since M4 and others have the same read speed, there's not going to be much difference. The only thing that would actually be any faster is sustained large volume writes, which is not something that most users do constantly.
Benchmarks are a good thing in many ways but they lead people to make massive assumptions based on headline speeds that don't correspond to real use. And the M4 is cheaper, which for some people will mean they can get a bigger one than they would have otherwise. Also you can update the firmware on a Mac.
I'm glad you are happy with your choice and knowing that you have the fastest is worth something, but for most people if you did a blind test in their own machine with their own normal use, they wouldn't be able to tell them apart. Right now I would probably go with the fastest too, but I'm not on a budget so the price isn't an issue. For a lot of people it is, though, especially as it's not much of a difference in real world performance.
by the weekend with any luck.
