I have worn Phonak for a long time. My first Phonak I think was a Picoforte in 1993. This was an analog model. Before that I had an Oticon analog for around 4 years, before that Philips. My 2nd Phonak was a Sonoforte 23 daz, still an analog but programmable this time, with twin directional microphones.
All of these aids, up to the age of 32, had exceptional sound quality, all wonderful with music but a nightmare in noise as @kevels55 will testify.
Then came digital and then admittedly some problems.
I was fitted with a Phonak Savia ITC by a danish audiologist which was underpowered but in noise it was surprisingly good. Perhaps due to still having the concha open to suppress noise. I wore that for 4 years before I demanded something more powerful, so this time I got the Phonak Savia BTE 211. On the next upgrade I went full circle when I saw that CICs were more powerful I got a pair - I think these were the Quest. Eventually I realised I needed a UP ITC set and upgraded to the Virto ITC SP. Again Phonak. In the last 4 years I then progressed to Phonak Marvel, Paradise and lumity rics (via Costco and specsavers white label models KS9, KS10 and the Advanced range).
In parallel to owning private Phonak aids, I was also fitted with Oticon aids from the NHS - Oticon Spirit Zest. They followed up recently with Oticon Dynano 8 aids, which are super power aids, and are excellent.
OK. So where am I going with this? I mentioned problems. I had a bad experience with the fitting of the Virto ITC SP because, fundamentally, the dispenser did not know what he was doing. After the fit, everything seemed OK, but when I went out, either the comfort in noise program would kick in, or the noise program would kick in, in a pub or other noisy environment, and there was this silence. So I would be in a supermarket, see the program “comfort in noise” and I couldn’t hear anything. It was just ridiculous. I went back to the audiologist and we tried making adjustments on 2 further occasions. I then realised the audiologist was not that competent and I then went to another, more experienced audiologist, who sorted the problem after 6 months.
So basically, I was to learn, there were 2 problems here and they both exacerbated the other. The first was that Phonak had at the time, although I believe it has improved since then, a notorious first fit. The fit I had with the Virtos was at least 12DB under what it should have been according to my prescription. The second problem was and still is to a certain extent (if you have a severe loss and are not wearing the BTE UP model) is that Phonak aids have a lot of noise reduction. So for me, I wasn’t getting enough gain to start off with, the problem was then confounded by Autosense programs like Comfort in noise etc.
The situation got better when REM was used for the Marvel, Paradise and Lumity. I would say that Autosense has worked well. As an Oticon wearer though I can comment that I have experienced one or two situations where the Oticon has proved to be better, particularly in the car. Fortunately, the NHS has always programmed the Oticons with REM, so they have performed well.
For me the bottom line is getting a competent audiologist with the most appropriate form factor for your loss. I cannot authoritively say that REM must happen, but I do know from experience that all the aids I have had programmed with REM have all sounded sharp and had a really good fit.
Take care, cheers Kev 
