I had a couple of HK's, three FAL's, and four M1A's, and of the three, the HK's would be my choice for an "overall" choice.
The M1A would be second, and you can keep the FAL's.
My HK's shot every bit as good as my similar grade M1A's, and were a lot more versatile when it came to accessories.
Ergonomics are a matter of familiarity and training. Once youre become familiar with the HK's (like the AK's), the so called problems tend to disappear. Its like anything else, you have to run the HK's like HK's, just like you run the others like they are meant to be run.
I still believe HK has the best all around "combat" iron sights, but you need to understand them and how they work. Many seem not to. Zeroing does require a tool, but once set, they are set.
With a good claw mount (HK or ARMS), the HK's are easily set up with zero repeatable optics.
If you use a port buffer, brass is easily reloadable, but it is shorter lived, or at least that was my experience. I usually only got around 6 loadings out of them, where I would usually get around 8-10 with my M1A's/M1's. Yes, the brass can get sooty, but the flutes only leave light scratches. I always tumble my brass, and it always cleaned up nicely.
I know a lot of people dont like the HK triggers, and they are an acquired taste. If you shoot revolvers, DAO autos, etc, I think the transition is easier. I do think its a mistake to have them turned into a tuned "American" trigger. My one buddy had Williams do his, and while they did a great job, what was done, was not meant for that type rifle, and I always felt it was unsafe for anything but bench or target type shooting.
If youre into "target" shooting, the M1A's are probably a better choice. I owned Standard, Bush, and SOCOM versions, as well as a NM rifle. The older M1A's (late 80's, early 90's) were the better rifles. The later guns, not so much. The SOCOM was my last, and between it, and the last half dozen or so 1911's of theirs I had, Ive sworn off Springfields guns all together. I wouldnt buy one unless I could shoot it first.
I had a bad run with the FAL's. My FN was "OK", reliable, and basically a decent gun, from a working standpoint, but it wasnt what I considered accurate. The others, meh. Aggravating would be putting it mildly. To be fair there though, they were early "kit" guns, and another hard lesson learned. No more kit guns for me, FAL, AK, AR.