At the moment I am using a 2015 15" MBP and no external monitor. It replaced a 2012 21.5" iMac which had become too slow and annoying. At the time I had been anticipating the arrival of the first 21.5" iMac with retina screen, but when it was finally released in the autumn of 2015, I was disappointed in the specs and after some research and much thought chose to go with the MBP instead, figuring that I would pick up an external monitor. I wasn't really doing much photo editing and haven't, really, until this summer, so now I am definitely thinking that I'll be making some changes in my setup this fall. I really like the flexibility of the MBP as opposed to an iMac and although I have desk space enough for a 27" iMac I just cannot wrestle one around physically, so would not consider that size anyway, it would have to be the 21.5" if I got another iMac, which is pretty doubtful at this point. My current MBP has 512 SSD and 16 GB RAM and so far that has been fine for image processing, and I use external SSDs (Samsung T series and a couple of G-Drive Mobile SSDs) for supplementary storage and backup. The Samsung T3s and T5s are the current/more recent backups and supplementary drives for everything and the G-Drives are used specifically for photography image files. Older external HDDs are now used just for archival files. I have mirror duplicates of my backups and my Photo files, with one copy of a backup and one copy of a Photo drive going to my safe deposit box at the bank each month.
I am considering one of the new 2018 MBPs with 32 GB RAM and 1 TB SSD, which should make a difference in speed when importing, editing and exporting image files, but yeah, they do cost a fair amount of $$$!!! Between thinking about that and thinking about a new camera, it's likely to be an expensive fall! I am also mulling over the idea of waiting to do anything about computers until we see what Apple has to offer in the way of iMac updates in the next couple months.
As for what I use for editing and processing images..... I have been using Aperture since its inception and arrival on the scene and I have been clinging to it even as Apple
stopped supporting it and even as we've gone though several versions of the OS where I could still use it. Up until this summer it didn't really matter all that much but now that I'm shooting much more frequently and in greater volume than I had for a long time, it's become a rather important issue after all. I've been trialling various programs and so far have purchased two -- Luminar 2018 and Capture One Pro 11 for Sony. I'm still trying to learn Capture One, but I really like Luminar. If they would only hurry up with that catalog/DAM they've been promising....
I'm not crazy about the idea of a subscription-based service so have not looked into Lightroom and Photoshop. I did use PS in years past but when Aperture came along I found that I was pretty much ignoring CS3, the last version of PS that I had, and so never updated beyond it and when moving to a new computer never bothered installing CS3 in it. Lightroom and Aperture came out at around the same time, and I vaguely remember doing a trial of LR and deciding that I much preferred Aperture, so never have looked at LR since then.
I also have Affinity Photo and Pixelmator but never quite felt at home in either of those, so they aren't getting much use. I also use Sony's Imaging Edge for looking at my RAW images from the RX100 M6, as that camera is so new that not every editing software has the ability to convert images from its RAW output yet. RAW Power does, and Fast RAW Viewer, though. I also have Graphics Converter and am planning to eventually use it to organize my image files much better. I'm also in the midst of a trial of Photo Supreme -- haven't yet made up my mind on that one, whether or not to purchase it.
Quite a while ago I downloaded the NIK Collection when it was still free from Google, but have never actually installed the program, either as a standalone or as a plug-in; probably won't bother now, as I haven't felt a pressing need for it.
Basically, at the moment I'm in a state of flux as I try out various options to find a good fit for me and my working style......
