Is it worth buying a 5009 given I require to rackmount the hardware? (I’m aware you can rack-mount the 5009 but they expect me to buy two or four units for this?)
The CPU runs slower on the 5009, is it faster than the 4011 overall?
Or is it mainly a switching performance difference?
I do see the 5009 is 64bits but is RouterOS taking advantage?
One thing to keep in mind is that for my local situation the 5009 costs almost twice as the 4011 does.
Naah, with a RB5009/L009 rackmount kit K-79 you can mount a single RB5009 in a standard rack:
https://mikrotik.com/product/rb5009_mount#fndtn-gallery
https://cdn.mikrotik.com/web-assets/rb_images/2071_hi_res.png
The list price of the two routers Is the same $219, It Is strange that on your local market the difference Is so relevant.
For the same price I would get the RB5009, as It Is new, arm64, etc., for double the price I wouldn’t be so sure, It depends on what you actually need.
What are your actual requirements?
I need to load balance two to three WANs the 3011 is barely routing the traffic at the moment and I had to remove most of the QoS, it’s at 90-100% now during full download speeds, I’ve outgrown it.
The 5009 has some sad design choices such as a front power connector, the rack option seems bendy unless you go with the full 4 stack?, I’m not a big fan of these designs sadly they’re super soho on the low-end side of things, I may be wrong…
I have a setup with single RB5009 mounted horizontally and another with vertical positioning (which is harder on the brackets).
No problems whatsoever.
As a side note: quite a bit of other devices (routers and switches) from Mikrotik use brackets to mount a single unit in 1U space.
Other brands do as well.
The difference with RB5009 (and L009) is that you can combine 4 devices in the same 1U space.
If you need to choose between 4011 or 5009, that’s a no-brainer. Always 5009.
I made the same decision several years ago (when the 5009 was very new). At that time, ROS 7 was not really ready for prime time, and the 5009 requires ROS 7. I went with the 4011 mostly because of the ROS 7 requirement with the 5009. I have been very happy with my 4011 and yes, it’s still running ROS 6. I do have a secondary router running ROS 7 so I can play with it and also for a WireGuard connection. One of these days I will move the 4011 to ROS 7.
this 
I’ve got a single 5009 rack mounted and it’s super sturdy (but at the same time single L009 mounted using identical kit in the same rack frame is kind of bendy, not a big issue anyway).
The 5009 has some sad design choices such as a front power connector
This. I’m still wondering in what setup someone would want to have the power plug sticking out of the front.
But the RB5009 has a screw terminal for power on the side which I usually use in rack setups to avoid having power barrel jack sticking out of the front, where it interferes with rack doors, SFP cabling and is prone to get unplugged or damaged during rack maintenance.
But still: Always RB5009: slightly faster CPU, 64bit, much better switch ASIC, 2.5GB Ethernet and USB3.
And our price situation is interesting: Usually the RB4011 is about the same price as RB5009.
And I just checked, currently at our supplier the 5009 (without PoE) is even 12€ less than the 4011 (without WiFi).
An RB5009 for twice the price of 4011 suggests the price is higher than usual. If possible, check if you can order RB5009 somewhere in Europe or Aisia
I would get the RB5009. Far more horsepower AND using a single switch design - with the SFP+ connected to it!
The RB5009 is MUCH easier device to deal with, no need to think about “these ones I put on that switch”, “those ones I put on the other”, “oh no, now I want to use the SFP+ grouped with those ports… but the traffic will cross my CPU!” With the RB4011 You will have to take all of this in consideration. The RB5009 uses a single switch chip for all ports - set them anyway You want.
Were you looking at the RB5009UPr+S+IN or RB5009UG+S+IN? In my distant market the RB5009UG is the same price as the 4011, but the RB5009UPr over 40% more, consistent with Mikrotik’s quoted pricing.