I would break this down further.I would definitely steer clear of any AC3200/AC2400 class routers at this point - AC1900 is still probably the best Price/Performance bet...
*AC5300/AC2600 is basically the same thing from a client perspective, just add one more 5GHz radio and associated $$$
AC2350/AC2400: First generation 4x4 Quantenna based "MU-MIMO Ready" routers. Replaced by 4x4 QCA-based AC2600 class with working MU-MIMO. I would not buy.
AC2600: Second generation 4x4 QCA-based with working MU-MIMO. Unlikely to significantly improve performance over AC1900 class. Buy only if you have MU-MIMO devices now or in the near future.
AC3100: Broadcom-based 4x4 router. Higher number comes from 1024-QAM support, which will only be useful with another AC3100 router in bridge mode. Supposed to support MU-MIMO when it appears. Products announced, but not shipping yet. I would not buy now even if they were because no MU-MIMO devices and too early on the learning curve for a brand-new chipset.
AC3200: Broadcom-based 3x3 "Tri-band" router with two 5 GHz radios and "Smart Connect". Smart Connect automatic band steering generally causes more problems than it solves in most implementations. Can be useful if you have a lot of dual-band capable devices and are willing to manually assign them to radios. Better to buy a second router, convert it to an AP and get improved coverage and total throughput utilization. If you really must two 5 GHz radios in one box, go ahead and buy.
AC5300: Broadcom-based 4x4 version of AC3200 architecture. Has all the negatives of AC3100 and AC3200. I would not buy.