Wi-Fi Signal Strength RT-AC86U v RT-AX88U

I wonder why the Wi-Fi signal strength on my RT-AC86U seems to be considerably stronger than on the RT-AX88U I was using yesterday (one of the reasons I sent the latter back for a refund)? The 2.4GHz never got above -33 and often fell to -39 or less and the 5GHz band also never made it into the -20's, but admittedly was more stable than the 2.4GHz range. The screenshots show what I am typically getting with my RT-AC86U which I find surprising given the difference in price. etc. The RT-AC86U...

Wi-Fi Signal Strength RT-AC86U v RT-AX88U