Re: AVH-P8400BH vs AVH-P4400BH
I think the major points have been covered, and I will confirm based off the dealer reference guide.
8400 adds - detachable faceplate, SD/SDHC card slot, 2nd rear USB input, H.264 WMV video format compatibility, MIXTRAX, dual zone audio/video, and advanced app mode. As kMethod pointed out, free navigation on the unit through your iPhone is a huge saving if you don't mind the constant data usage.
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