Does anyone know if the 4200nex has a higher amp output than the 4100nex. On my 4100nex max out put for usb 2 is .5 amps. My 410pnex has a hard time pushing data thru the cable using a usb mount and a USB standard 4' samsung cable. I understand that amperage has nothing to do with data. But it may be able to amplify the singal sending and receiving. I notice the new kenwood 9903s has fast charge up to 1.5 amps

I am in the market for either the 4100 or 4200 right now so I kind of have the same questions.  I have been leaning toward the 4100 since there are not any significant changes that I can find and the price is lower.  Actually the only thing that is holding me back is the thought of having reduced charging speed.  I have a Nexus 6P and I have gotten very used to rapid charging.  I have 3 amp chargers everywhere now including my car and it is really convenient.  I feel like I never worry about low battery anymore.  I tried to research this myself and in looking at the spec sheets for both the 4100 and the 4200, the USB current is listed the same at 1.6 amps.  I did find one post where a 8100 user claims they were getting quick charging on a Nexus 6P.  That normally requires at least 2.4 amps from my experience.  BTW, the 8100 spec sheet also lists 1.6 amps as the USB output.

Your comment that the 4100 is only providing .5 amps has me even more concerned.  How did you determine this?  And what phone are you using?

None of them do the fast charge... maybe in a couple years the HU's will come with that

I'm using a not 5 with the original whit samsung cable and max amps being pulled with nothing runNing is.610 amps with android auto it dips to about .19 amps charging with android auto running. All this is without the extension cable pioneer provides.

I am using an amp called ampre which seems to be highly rated and accurate.

I'm sorry I misinformed all of you. The 4100nex provides 1 full amp. I was stupid and plugged my phone in with a almost full charge. I was able to get 1 amp with a 6ft usb extra and the 4 ft samsung cable. The problem I'm having lies with the app itself. Every week or two I have to reinstall the app. Once the app reinsallspice everything works flawlessly.

Just to follow up on this, I went for a 4100 and installed it last weekend.  I tested the charging with my Nexus 6P using the Ampere app (same as OP).  I get between 300 and 1000 mA and it fluctuates between them mostly in the 400-800 range.  For reference when I charge my 6P with the OEM wall charger, I get 2400 mA consistently (and it charges hella-fast).  The good news is that even with the lower charge current, it is sufficient with my device to not only maintain battery level, but actively charge while I run Android Auto in the background and Waze on the phone with the display on full time.  This is good enough for me.  I am satisfied!

I bought one of those AC port adapters (used to be call cig lighter port) that does the fast charge, for days I need it... otherwise, you are right, it's enough to keep it changed