RouterOS is very stable. I've been running it for 10 years (in a few months) and I've not once come across an issue due to RouterOS.
I've encounter other issues but it was due to the hardware (faulty internal 3.3V supply, which I've fixed) and not due to the RouterOS.

I can say it's on par or even more stable than IOS (not iOS). 
Btw, I run v6 Long Term code.

Anynone here want to letgo their RB5009? So hard to find one locally used or new.

Already mesaged them. Waiting for restock around July

For malaysia vlan ipv6,u can follow this guide- https://forum.lowyat.net/index.php?showtopi...&#entry63945436
If not strongly needed for ipv6,better do not enable ipv6 on unifi now.(maybe next year or next 2 year better,now still not stable enough to use)

Mikrotik IPv6 does not support fasttrack now,it will be implement in ROS7 future version but still does not have timeframe for it,so i think next year or next 2 year should be getting IPv6 fasttrack on mikrotik.

Currently,for RB5009 without ipv6 fasttrack,the cpu usage to use full 800mbps unifi is around 25-35% for 800mbps download,and around 6-12% for 200mbps upload.

I have to differ.
I don't recall having much issues with IPv6 on UniFi previously (since 5Mbps days, then 10Mbps) 
No issues on TIME now too.

All my supported end devices have global IPv6 addresses, been running this for many years.

I usually use this to test IPv6 connectivity, unless there's any major issues, it's 10/10.
https://test-ipv6.com/

On Tests Run tab,
Test with IPv4 DNS record   
ok (1.032s) using ipv4
Test with IPv6 DNS record   
ok (0.820s) using ipv6
Test with Dual Stack DNS record   
ok (0.813s) using ipv6
Test for Dual Stack DNS and large packet   
ok (0.333s) using ipv6
Test IPv6 large packet   
ok (2.110s) using ipv6
Test if your ISP's DNS server uses IPv6   
ok (1.390s) using ipv6
Find IPv4 Service Provider   
ok (1.091s) using ipv4 ASN 9930
Find IPv6 Service Provider   
ok (0.929s) using ipv6 ASN 9930
Other IPv6 test sites,
https://ipv6-test.com/    <- I get 19/20 on this, because there's no reverse DNS record.
https://ipv6test.google.com/

i looking good Mikrotik router

my office 5x PC i looking block some website let say 2x PC or 3x PC always use Lan Cable not wifi

can do block 100% let say facebook block and youtube block and etc

due staff enjoy access without work

my office using asus router always failed some not supported https that can be access waste

V7.6 on RB5009. Internet a bit more stable. Gamer can feel the different.