The big difference is the Herpstat II has two seperate channels. It's like two stats in one package. I don't have any Herpstat II's but I do have several of the Herpstat Pro's. The Pro is a four channel unit and comes with four seperate probes. I use them to control cage stacks precisely. No vertical temp differential since each level or group of levels has it's own controller. I absolutely love the Herpstat Pro's and would recommend them to anyone. Looks a little pricey at $300plus but not pricey at all when you consider it's actually four seperate controllers with built in night drop!!
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Thanks,
Dave Colling

www.rainbows-r-us-reptiles.com
0.1 Wife (WC and still very fiesty)
0.2 kids (CBB, a big part of our selective breeding program)
LOL, to many snakes to list, last count:
24.36 BRB
19.19 BCI
And those are only the breeders 
lots.lots.lots feeder mice and rats 

