The RPi4 CPU is also a bit more powerful.
But I think @nerdatwork is right: the main issues with RPi3 are:
- not enough RAM to be future proof, although mine is not using more than 400MB right now (but more is always better as linux makes use of ‘free’ ram for caching many things to be faster).
- 100mbps ethernet, although that’s probably enough for STORJ - My RPi rarely goes above 30mbps when uploading/downloading pieces of data. For now at least…
- USB2 only - however I think it’s not a real issue as the ethernet connection will be the bottleneck. Maybe it could slow things down a bit if you were to plug many hdds to it… For me the real problem with RPi usb ports (RPi 3 and 4) is that they do not provide proper power for plugging 2.5" HDDs.
On the other hand, I do not have the figures but I guess that RPi3 consumes less power and stays cooler than RPi4 (mine is above 63°C at all time despite some small heatsinks installed, and we’re in winter… Not sure how it’s gonna be during summer).
If I were you I think I’d give it a go to see how it performs by closely monitoring RAM, network & cpu usage. It’d nice to check its T° and power consumption too. And if everything looks good after the vetting period, then maybe it’s not worth buying anything for now: use what you already have, that’ll be more profitable.
And if something is off, then you could always buy a RPi4 later if you wish.