I have an IP4 and I love it. Of course, the IPV3 Li came out like a week after I bought the IPV4, however, I can't complain because the IPV4 does everything I want it to do and more. The only advantage for me would be having the titanium mode and running it up to 100 joules in that mode, but that upgrade might come out for the IPV4 soon (Although it will not have 200 watts in wattage mode, which I would never use anyway). Overall, I like the idea of having a Yihi board for under 80 dollars.
I think between the IPV4 and the IPV3 Li it would come down to your subjective taste/preference for the looks and if you want to use titanium right away. I have no experience with the Snowwolf, but it was something I considered but it was a lot more expensive when I bought the IPV4. I would have had a much harder decision if it was at the price it is at now and probably would have went for the Snowwolf because it can go up to 70 watts with nickel and I prefer the looks, however, I would be concerned about finger prints on the sides driving me crazy on the Snowwolf (caveat: I have never actually held one).
I can't comment on the Sigelei 150TC, but would think that is more comparable to the IPV3 Li.
I think with any of the devices you listed that you would have a great experience.
