Which external flash works best with Canon mirrorless cameras?

Seconding the recommendation above! I moved to the Godox V1-C Flash for Canon and it's a beast. Honestly, the lithium batteries are way more reliable than AAs because they don't overheat or leak during long events, which is a huge safety plus for me. Also, check out the Godox V860III-C Flash for Canon if you prefer a traditional head; the newer metal mounting foot feels way more secure on the R6 shoe. gl!

Can confirm

I went through this last year! Over the years I've tried many flashes, and honestly, the jump to mirrorless makes the market feel totally different. Like you, I felt that weird communication lag with the Canon Mount Adapter EF-EOS R and my old speedlites... it's highkey frustrating. I did some research and here's basically how I saw the options:

* Canon’s New Gen: The Canon Speedlite EL-5 mentioned earlier is the "pro" choice for that specific shoe, but it's so heavy. There's also the Canon Speedlite EL-10 which is way lighter, but maybe not powerful enough for high ceilings?
* Third-Party Options: The Godox V1-C Flash for Canon is popular because their lithium batteries mean you arent carrying 20 AAs anymore.

I found the recycle speeds on the lithium units are actuallyyy faster than most AA-powered ones. Tbh, the balance on the R6II felt a bit more natural with the Godox for me, even if the build quality feels a bit different than the tank-like Canon stuff. I think? Anyway, just sharing what I found! gl!! 👍

TBH if the EL-5 feels too chunky for you, check out the Canon Speedlite EL-10. It’s pretty much the modern mirrorless version of your 430EX - way lighter and it slides right onto the R6II shoe without needing an adapter. Another sleeper pick is the Godox V860III-C. Its got the same lithium battery as the V1 everyone loves but uses a traditional square head, which I think balances a bit better on the R-series bodies. Plus, that built-in modeling light is SO helpful for focusing in dark reception halls! Just keep in mind that since the R6II has that new multi-function shoe, staying native with the EL series usually gives the most reliable HSS performance without any weird glitches.

Building on the earlier suggestion, it really seems like shifting toward those lithium-powered units is the way to go for the R-series. I have been pretty satisfied with how they handle recycle times compared to my old AA sets. It just works well without the constant swapping. I did want to add a few cautions based on what I have seen lately though:

• Watch the pins on that R6II multi-function shoe. They are way more delicate than the old style. If you are swapping flashes in a hurry, it is easy to accidentally bend something or get dust in there that messes with the TTL.
• Try to avoid the super cheap off-brand battery clones. Stick to the official ones for whatever brand you pick. I have heard stories of the cheap ones swelling up inside the flash, and that basically ruins the whole unit.
• If the balance is still bugging you, maybe look into a basic flash bracket. It is a simple DIY-style fix that moves the weight off the top of the camera and onto a side grip. It makes a huge difference for your wrists during long family portraits. Glad to see everyone moving away from those bulky adapters... they are fine for a bit but a direct connection is just way more reliable for events.

> ...which external flash do you think offers the best mix of size, recycle speed, and reliability for Canon mirrorless users right now?

Unfortunately, the Canon Speedlite EL-5 was not as good as expected and felt way too bulky on my R6II. Honestly, the Godox V1-C Flash for Canon is the sweet spot for size and recycle speed. Lesson learned: that round head gives way better light spread for bouncing and ngl, its basically more reliable than my old setup!