It really depends on your usage, I think you might have sent me the message on reddit but if not, PM me and I'll get with you on what I think fits best for your usage.
I have a hexohm V1, and it's a close tie between the HexOhm V2 and IPV3 I believe. I prefer my hexohm V1 over the sigelei 100 slightly as far as performance and vape quality and versatility with my usage. The DNA40 is completely different from the Sig and IPV though, and I'm a HUGE evolv and authentic DNA fan.
If you like building coils with large gauge wire, blowing huge clouds and building in general and have been using mechs and are familiar with battery care and safety, the HexOhm V2 might be for you. It's a beast and the punch and vape quality overall is amazing on the hex. If you're just getting into building or considering getting into it and use tanks and such, and just care to blow average clouds (for today, which would be bigger than big clouds a few months ago) if you're building, then you might want to look into the DNA 40.
The DNA 40 has the battery meter and temperature control, and really the Evolv authentic quality and technology is the only reason I'd say to choose one over a hexohm. If the screen is really the only difference and you're looking at some of the other non evolv chips, I'd go with the HexOhm V2.
The 510 connection on the V2 is amazing, so unless you get a really good deal on a cheap V1 or find one with the fat daddy vapes 510 connection, I'd stick with the V2 as far as difference between them. Also if you build really low ohm builds, the amp limit on the V2 is a reason to get it. But the vape quality is so good with a V1 and .35 to .5 ohm coil with the increase surface area, I don't think the increased amp limit is "needed" although it's nice to have.
PM me if I can be of any more help, it really comes down to the user and how they plan to use it, the DNA 40 and HexOhm are two of the best available mods in my opinion and preferences and needs determine what will suit you better.
One last thing, if being away from a charger for long periods of time is a feature you'd like to have, look into dual 18650 versions of the DNA 40, having a few days of battery life is nice, and an advantage of the hexohm over single 18650 battery mods, but an easy remedy.