I'll just comment on the mods that I own or what close friends have.
rDNA40
It is one of the first boards to feature temperature control, groundbreaking just a year ago. Had a rocky start initially; glitchy screens etc. However it has all been refined and is now one of the more stabler mods. Prices have started falling down for DNA40 devices, such as the Vaporshark rDNA40 and DNA40. Think it is now like USD$130? Cheaper DNA40 mods are available too such as the Hcigar HB40.
I've been using a rDNA40 for about a year now. Compared to the newer chips it still holds its ground despite its relative age. Accurate temp control, accurate resistance readings. It only has a nickel mode though you can fire titanium but you've to compensate for temperature. Paint chipped quite a bit though i'm sending it to be powder coated soon. Zip charging is fantastic. Charges my LG HG2 3000mah batt in about 100mins. Great device if you don't need lots of power.
IPV D2
A very recent acquisition. It uses the (Edit: SX130H chip, thanks Eugene) It is tiny. Smaller than my vaporshark definitely. About the size of the istick 50w. It is quite well built, though the paint is thin and scratch easily. Luckily they provided a silicon sleeve. Don't really like the barrel pin charge port but it works well. The board works well; accurate temp reading and resistance reading and has Ti & Ni modes. More powerful than DNA40 since it goes to 50joules or 75watts. Make sure you get at least a 20amp batt to reach full power.
Evic VT
The evic VT is kind of in neither camp. If i am not wrong their chip is proprietary. The chip isn't as good. In wattage mode it functions perfectly. In temp mode you can only use 30w to 60w. Nothing lower than 30w. Shame really since i usually go 20w. I also don't like how you can't easily increase or decrease the watts in temp mode. You can only increase, and it rou robins after hitting 60w. Kind of irritating. Nevertheless, temp control works fine, has both Ti & Ni modes and the battery life is superb with the 5000mah batt. Love the built quality and paint job + that gorgeous screen.
Sigelei 150w.
Big and powerful, it swallows 2 18650s. Chip reads to 150W and it has temp control for both Ni & Ti and it works well. Nice rubber coating. Nothing much else to say about this. Big and powerful.