Saw your post and honestly, you arent alone. Weddings are high-stakes so I get the nerves about switching brands. Ive used both and heres the deal. The Canon Speedlite 600EX II-RT is basically a tank. If you are shooting in a monsoon or need 100% certainty that every TTL pulse is perfect, thats the one. But $500 is steep if you arent doing this every weekend. The Godox V1-C Flash for Canon is what most wedding pros are actually using now tho. Its reliable enough for pro work, but you gotta know the quirks:

• The round head is cool but mostly hype for the softness, it just makes light fall off more naturally at the edges.
• The Godox VB26A Rechargeable Lithium-Ion Battery is the real MVP because it lasts forever compared to traditional AAs.
• TTL on Godox is about 95% as good as native Canon. You might get a tiny bit of drift but nothing like the Yongnuo headaches. If you want to save even more, the Godox V860III-C Speedlight is basically the V1 but with a traditional square head. Its a bit cheaper and works just as well. Just make sure you update the firmware first... that fixes most of the weird TTL bugs people complain about. Since you have three weeks, buy it now and test it in a dark room at home first so you trust it before the big day.

honestly i am super happy with the Godox TT685II-C TTL Flash for Canon DSLR and havent had any issues. yeah i thought the same about budget flashes but the ttl on these is so much better. if youre trying to save money for the wedding i would just go this route. works well and way cheaper than canon... no complaints from me after a year.

ngl you definitely notice the difference when you stop using the budget stuff. i had that same issue where half my shots were blown out and it was a nightmare. i eventually moved to a model with a better battery system and the consistency was night and day. honestly, having a flash you can actually trust for a wedding is worth every penny.