Hi
I am a former ACDSee user, I also have extensive experience with CaptureOne, Adobe Lightroom and Photoshop and now DXO Photolab is my main tool.
I have 2 Macs: an M1 Mini with 16GB RAM and 512GB SSD and an M2 Pro MacBook Pro, also with 16GB RAM and 521GB SSD.
Firstly, 16GB RAM is absolutely enough for photography. I invite you to watch
this video , my experience is identical, I never notice any slowdown. I have no idea how much swapping is going on but the Mac reads and writes from SSD at 3GB per second, making the issue irrelevant in my opinion.
Regarding disk space it is all a matter of how you organise your storage. I have a NAS and I put as much as I can on it. My 512GB SSD has a usable capacity of 494GB, of which 406 is available.
For the CPU, I find the M2 Pro feels marginally faster than the M1. The M2 Pro slaughters the M1 in benchmarks, but in real use I cannot say it makes a huge difference for me. I use both very happily. It might come from the fact that DXO does use the Neural Engine, which maybe lessens the perceived difference between the two.
To put things in perspective, when I got he M1 Mac mini, I had a PC with the following components: AMD Ryzen 8 cores 16 threads, 32GB RAM, 1TB MVME SSD and an AMD Radeon Pro graphic card. In Lightroom and Photoshop, the M1 was way faster. Not a subtle difference like between the M1 and M2, it really felt like a new generation of hardware.
I would expect a current Mac Mini M4 to be a blast.
Software-wise, Lightroom and Photoshop are the best in my opinion, but I have decided to stop using the subscription, mainly because I don't want to have to continue spending if I ever go through a rough patch.
Of the alternatives, Capture One and DXO are both of very high quality, with different strengths. In the end, I went with DXO and am very happy with it. I probably would be happy if I had chosen Capture One too.
There is the fact that Capture One pushes more towards the subscription model that DXO, who have no subscription in sight.
Capture One subscription model is more honest than Adobe's. It gives you a progressing discount on a perpetual license with each year you keep the subscription. After 5 years you receive a free perpetual license that you can use as a backup plan if and when you want to stop using the subscription.
Good luck with the decisions
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Stéphane