Linksys wrt3200acm 1.8ghz dual core VS Asus AC58U 717mhz quadcore

High-end mvebu and entry level ipq4018 (with a price delta of roughly a factor of 4) don't punch at the same weight level, although each have some advantages over the other, where they can outshine their opponent.

The ASUS RT-AC58U however is a bad example for the ipq40xx SOC, as it's (too-) short on RAM (128 MB for two ath10k 802.11ac radios is not sufficient), most other ipq40xx based devices ship with at least 256 MB RAM instead.

In general, mvebu is (much) faster in terms of routing throughput (WAN speeds), coping with up to 1 GBit/s easily - while ipq40xx is less picky in terms of WLAN interoperability (mwlwifi is known to have problems with IoT devices (esp8266)) and probably better in this regard (despite being worse on paper (two rx/ tx chains compared to three).

It really depends on your requirements, the WAN speed (both now and within the immediate future (3-5 years)), what additional services you intend to use (SQM/ VPN) and your emphasis on wireless reliability.