I used to buy only DD-WRT routers and vouch for them all the time, but since 2016 APR, non of the versions worked with DDNS and a lot of the versions would softbrick and be stuck on what ever version was flashed at the time till I 30/30/30 and reverted to stock or tftp the damn thing. Not to mention DD-WRT hard crashing when ever it hit near 3K connections.
Bit the bullet and flashed the ones that were compatible to OpenWRT and while it took a considerably longer time to set up and needed packages for every little thing like UPNP and multiple packages just to get samba working, it's been able to handle around 5K connections without hard crashing although LUCI would still become unresponsive until the number of connections went down.
My main router runs Merlin though as it's just easier to use.
Currently personally use.
Asus RT-AC68U, Merlin, main router.
TP-Link TL-WR1043ND, OpenWRT 18.06.1, main router at shop, also handles light NAS duty separate from the main storage server.
DLink DIR-825 B1, OpenWRT 18.06.1, backup router.
DLink DIR-600 B1, OpenWRT 18.06.1, can't handle 100mbps througput.
Also have used,
TP-Link TL-WR841ND, stock firmware, super cheap, no frills, just works.
TP-Link C1200, stock firmware, can't flash, for the love of god don't buy this pile of shit, usb storage functionality is incompatible with non latin characters and just fucks everything up.
DGL-4300, stock firmware, pretty good at the time, basically melted and died.
DI-514/524 Had a lot of these dinky little things back in the 802.11b/g days, have a friend that still have 2~3 of these in low traffic areas around his 5 floor home with better routers doing the heavy lifting.
Asus RT-AC1300UHP, friend bought this for his new home for 36% off, doesn't seem to be flashable, but hey, I set it up for him, 8 wifi devices, 2 computers, a TV box and a PS4 on a 100M/40M FTTB line and he's happy.
A few Tendas which had no firmware support or many functions but they didn't seem to crash.