OK, here are my experiences. First, a bit of my history.
I started wearing 1 Siemens CIC aid for 3 years. I then moved on to a pair of Widex Diva ITC aids for 7 years. Last year, I tried a couple of Phonak BTE aids, first open fit & then with custom molds. A while after returning them, I tryed some open fit BTE aids from Hearsource. I am currently wearing Micro Tech (Starkey) CIC aids.
CIC vs. ITC aids: the user tends to have a better sense of the direction of sound with the CIC aids. Battery life appears to be slightly shorter with the CIC size 10 battery vs. the ITC 312 battery.
Depending on the programming, the BTE aids can have issues with wind or, perhaps, long hair rubbing the aids.
My ITC aids have telecoil & button, so phone was not much of an issue. The BTEs also had either an automatic telecoil or phone program, but you needed to hold the phone a little higher on the ear than normal. My current CIC aids have a phone program, but I do not find it very helpful.
The BTE aids generally can fit more severe or unusual losses that CIC aids. If a receiver (speaker) goes bad with a RIC aid, that is generally a standard part stocked by your professional. CIC and ITC aids need to be sent out for receiver issues.
For the BTE aids I trialled, I do not believe the Phonak aids were properly programmed for me. The Hearsource aids were a lower end product and had feedback issues.
Many professioanals here prefer the BTE style aids for their patients. I sometimes wish I had tried BTE/RIC aids before my CIC trial ran out. I am currently without one of those aids for the second time since June.
I hope my rambling helps.
EDIT: I see one of them, ZCT, answered you while I was typing this.