Honestly, I have been shooting weddings for years and made the switch to the Godox V1 Canon TTL Speedlight a while back. I was worried too, but it has handled thousands of shots without a hiccup. The round head gives a nice falloff thats way softer than the traditional rectangular ones. Just be careful with the hot shoe on the V1 tho, it can be a bit fragile if youre rough with your gear. If youre really stressed about reliability, maybe look at the Godox V860III-C Speedlite as a backup. It uses the same battery system which is a lifesaver. You definitely dont need to drop $600 on the Canon Speedlite 600EX II-RT right now, especially with a $400 budget. Just make sure to get a spare battery because once that li-ion dies, you cant just swap in AAs. Youll be fine, just keep an eye on your heat levels during heavy dancing sets... you got this.

Oh man I totally feel the wedding nerves!! I saw this earlier today and just had to chime in because I went through this exact same panic last year. If you are worried about reliability but dont want to drop $600 on the Canon name, I am obsessed with the Godox V860III-C Li-Ion Speedlite for Canon right now! It is basically the V1 but with a traditional head and it is such a fantastic workhorse. Honestly, the best way to stay safe is to buy two of them since they are so cheap compared to Canon... that way if one fails (it wont!) you have a backup ready to go.

• the battery life is actually insane compared to AAs
• way under your $400 budget so you can actually afford a spare
• built-in modeling light is a lifesaver for focusing in dark churches I used to be so scared of non-Canon stuff too but these things are amazing! Just grab an extra Godox VB26A Rechargeable Li-Ion Battery and you are literally set for the whole night. Youre gonna do great!!

I saw your post from yesterday and totally get the stress!! Weddings are high pressure and you really dont want gear failing when the bride is walking down the aisle. Years ago i was a total Canon purist because a cheap flash once literally died on me during a cake cutting... super embarrassing! But honestly things have changed so much. If you want something ultra reliable, look at these:

• Godox V860III-C TTL Li-ion Flash for Canon
• This thing is a total beast!! It uses a lithium battery so the recycle time is insanely fast. The battery lasts forever too, usually a whole wedding on one charge!
• Westcott FJ80 II 80Ws Universal Speedlight
• This has fantastic build quality. I love it because the thermal management is amazing, it just doesnt overheat during heavy dance floor sets. Youll be totally fine with that 5D IV, its such a fantastic body! Just get a spare battery... i always carry extras because im paranoid lol.

Honestly its just getting ridiculous with these prices lately. I feel your pain so much because it feels like the industry is basically forcing us into a corner where we either spend a months rent on a single light or risk everything on something that might just snap in half. Its such a scam.

• Big brands charging a massive premium just for a logo while the build quality feels cheaper every single year
• Third party brands being supposedly pro-grade until they fail at the absolute worst possible moment
• The constant anxiety of gear dying mid-ceremony becoming the new normal for wedding photographers It is just exhausting, honestly. I wish these companies actually cared about photographers who are just trying to make a living instead of just squeezing every penny out of us... it drives me crazy.