MacOS – High memory usage on MacBook PRO retina 16Gb i7 2,5ghz

Your information is very good for RAM and CPU, but I don't see anything amiss and things look quite balanced. Yes, there is one program that's busy and not responding, so you could kill that to rule it out as something that's slowing down Photoshop.

My hunch is you will need to examine storage to find the slow down.

My reasoning is Photoshop does a good job of pre-allocating disk space for swap of it's own (so it doesn't even swap to the OS swap) as well as pre-allocating all the RAM it thinks it will need. Even without seeing the normal RAM and CPU charts you posted, it's unlikely your Mac is paging virtual memory to disk based on the stats you posted from a snapshot in time.

Open terminal app from /Applications/Utilities and run two commands to list the attached drives (so you know which is disk0, disk1 etc...) and another to monitor the actual input and output for the drive.

df | grep disk
iostat 30

The second command will run continuously until you press control+c or close the terminal app or window.

My guess is you will see that there is continuous load on one or more disks and quitting the programs that are causing the disk to be busy will make Photoshop more snappy. You've already ruled out high CPU load and memory contention (the pressure would be yellow or red if that were to slow down Photoshop) so the next likely candidate is that the system is waiting for the storage.

The other suggestions to try killing other applications are good ones, but you will be more successful if you can measure the exact slow item and then change things and re-measure later.

Here is a sample of what you might see on an idle system:

Mac:~ me$ iostat 30
          disk0           disk1       cpu     load average
    KB/t tps  MB/s     KB/t tps  MB/s  us sy id   1m   5m   15m
   36.80  20  0.71    24.99   0  0.00   6  3 91  1.34 1.61 1.65
   32.00   0  0.01     0.00   0  0.00   1  1 97  1.32 1.60 1.65
    0.00   0  0.00     0.00   0  0.00   1  2 97  1.37 1.61 1.65
    4.00   0  0.00     0.00   0  0.00   1  2 97  1.31 1.58 1.64
   28.57   1  0.04     0.00   0  0.00   4  3 93  1.48 1.61 1.65
    9.85   3  0.02     0.00   0  0.00   2  1 97  1.44 1.60 1.65

Here is what first a minute of activity on the internal SSD then idle, then a minute of activity on the Time Machine drive and idle, and finally Time Machine running with both drives having equivalent activity (read from one = write to another):

Mac:~ me$ iostat 30
          disk0           disk1       cpu     load average
    KB/t tps  MB/s     KB/t tps  MB/s  us sy id   1m   5m   15m
   36.95  20  0.71    42.93   0  0.00   6  3 91  1.99 1.90 1.75
    8.1 1266 10.09     8.00   0  0.00   8 12 81  1.94 1.89 1.75
   10.18 774  7.69     0.00   0  0.00  22  9 69  1.64 1.82 1.73
   18.42 125  2.25     0.00   0  0.00  11  4 86  1.50 1.77 1.71
   32.27  21  0.67     0.00   0  0.00   6  2 92  1.40 1.73 1.70
   12.29  48  0.57     6.78 223  1.47  23  8 70  1.74 1.78 1.72
   20.30  14  0.28     9.61  53  0.50   2  3 95  1.39 1.69 1.69
   17.73   5  0.08    14.75   0  0.01  11  2 87  1.23 1.62 1.66
   32.30  23  0.73     0.00   0  0.00   4  2 94  1.50 1.67 1.68
   13.14   3  0.04     0.00   0  0.00   6  1 92  1.45 1.64 1.66
   21.07  24  0.50     6.12   0  0.00   9  3 88  2.23 1.80 1.72
   40.77 197  7.86    37.93 202  7.47  13 10 77  2.27 1.83 1.73

Here's the way it goes in our household:

I own the 15" Model you describe above (albeit a slightly earlier version with the GTX750M GFX card) and my other half has the 13" you describe above (again, albeit 6 months old at this point)

Now, she does a lot of graphical work on it in Adobe CC - Photoshop, Illustrator, InDesign, etc - much the same as you want to. She says it never skips a beat for her, even when she's running it on external displays in the office and driving the graphics side of things hard. She sometimes gets frustrated with the lack of screen real estate compared to mine (when she does use it) but it's generally not a problem for her. The battery also performs a bit better, which helps if you're on the move a lot. Sure, a bit of extra power would help her but the portability and price trade offs aren't worth it.

Based on what you've said, I'd recommend the 13". It's plenty powerful for what you want, but I would use the left over cash to buy a couple of nice 24" external displays if you have the space to set up a small office. I love having 3 displays running (1 on the MacBook + 2 external.) Better on so many levels!

Another note - it used to be possible to upgrade MacBooks (more RAM, swap out the HDD for an SSD, etc) so I used to recommend buying less and adding to it when you need it. Can't do that anymore, so buy as high spec as you can afford.