It is just my opinion as I have not used either yet (my IPV4 is on the way) but I would go with the IPV4. Unless you are a cloud chaser, there is no reason to go for 150 watts. I had a similar decision as you, and chose the IPV4. For me, it was between the IPV4, IPV3, or Snow Wolf 200. I didn't even consider the Sigelei as I've heard a lot of negative opinions about them from local people, but YMMV there. Anywho, I decided on the IPV4 based on reputation, looks, performance, and cost. I have an 80 watt device now that works great for me, but when I do a .1(sih) build, I wouldn't mind a little more power but that's just me. I also wanted temp control (and one that worked!) as well as just another box in genera to have around so I'm not alway swapping tanks. Hope this helps!