If you look at ASUS's feature comparison, you don't see much difference between the GT and RT. The GT supports link aggregation, while the RT doesn't. But both support Traffic Analyzer, Adaptive QoS, AiProtection and Parental controls. The comparison table is obviously flawed, since it makes no mention of WTFast and Game Private Network supported by both.
The larger comparison omission is the GT's VPN support, which is the same as the RT's and includes both PPTP and OpenVPN servers and PPTP, L2TP and OpenVPN client.
GT-AC5300 antenna key
The short story here is if you're looking for game-specific support, you already have most of what the GT has if you already own an RT (minus the kewl gamer GUI look). The GT just moves things around a bit. You'll find QoS and Traffic Monitor under Game Boost on the GT, but that menu on the RT holds WTFast, LAN Boost (a quick configuration of Adaptive QoS) and AiProtection jump points. The unique things the GT brings to the party are the dashboard...
...Game Profile (aka port forwarding presets for games)...
GT-AC5300 Game Profile screen
...and Game Radar and Wi-Fi Radar menus. Game Radar shows ping times for popular game servers. But you can't change the Game list or server locations.
GT-AC5300 Game Radar screen
Wi-Fi Radar contains tools commonly found in the many Wi-Fi scanning apps available. I give ASUS an "A" for effort, but an F for implementation. Each icon shown below takes you to a tab on the same screen.
GT-AC5300 Wi-Fi Radar screen
The screen shows only one radio at a time and is very long, requiring a lot of scrolling around. I homed in on Channel Statistics.
GT-AC5300 Wi-Fi Radar Site Survey screen
The problem with all Wi-Fi troubleshooting apps to date is that they don't measure channel use. They can tell you how many APs are in range, channels they're on, signal strength, etc. But they can't tell you anything about the activity in each channel, i.e. how busy it is. Channel activity, not signal strength, is what you want to avoid in neighboring networks if you want maximum bandwidth.
Unfortunately, ASUS does not appear to be measuring channel capacity, either. I ran a quick check by blasting traffic on Channel 40 on one 5 GHz radio and Channel 153 on the other, using 80 MHz bandwidth for each, which takes up four 20 MHz channels.
The octoPal client reported channel congestion (use) in the 90% range for each channel. But Wi-Fi Radar said over 80% of the capacity in each channel was available! The bars below should all have been 10% or lower.
GT-AC5300 Wi-Fi Radar Channel Capacity screen
The Advanced Troubleshooting tab supposedly offers plots of all the Wi-Fi statistics shown. Just the ability to see packet retries alone would be a huge help in troubleshooting Wi-Fi connection problems.
GT-AC5300 Wi-Fi Radar statistic categories
But the only categories working right now appear to be Rx CRS Glitches, Bad PLCP and Bad FCS shown below. The User manual is no help for any of this, so you'll need to hit your favorite search engine for definitions. (Hint, these aren't going to help much with determining why your client keeps disconnecting.)
GT-AC5300 Wi-Fi Radar statistic plots
ASUS clearly has more work to do here. The erroneous Channel Capacity "feature" is going to cause a lot of unnecessary confusion and frustration if people try to use it.
The Router Charts graphs below show storage benchmark write and read results using our standard procedure with USB 3.0 connections and NTFS drive format, for the four products tested so far with the Revision 10 process. I made sure the Reducing USB 3.0 interference setting in the 2.4 GHz Wireless Professional settings tab and iTunes, DLNA and FTP servers were all disabled before running the tests. I even rechecked the RT-AC5300, running USB 3.0/NTFS tests only.
There is obviously still something wrong with the RT-AC5300's USB 3.0 connection, given it yielded only 31 MB/s write and 34 MB/s read. But whatever's wrong with the RT has been solved with the GT, since it produces much higher throughput.
Storage Performance Comparison - USB 3.0 / NTFS
The GT isn't best in class for storage performance, however. Switching to the Chart Revision 9 view shows Linksys' WRT3200ACM still claims the top spot, producing over 100 MB/s for both write and read. You can compare storage results between Revision 9 and 10 processes because the Storage test process hasn't changed.