Hey :)
I'm really not too sure to be honest because I only have the wide and original Straightener. I would just go with the original one for your hair because it's going to give you amazing results and I can guarantee you that :)

If you wanna know more about the simple touch and types of straighteners like the differences then GlamPalm has their official website with their contact phone number. I normally use to just call them up and ask them everything. They're such good help :)

The simple touch is a new line of motion detection so instead of turning your iron on and selecting your settings there are preset setting that are available by touching the plates together. While this is a revolutionary design if you have a specific hair type that requires a certain temperature and styling I would chose the original which still has the same expert quality plates as the new design as your hair is mid-length sweetie and have a thin hair the original straightener would be perfect for you. Hope this helps

The Classic Series come with 11 heat settings, a heat proof clutch bag, dual voltage and a 3d-swivel pivot cord 30 min. auto shut-off..
The SimpleTouch has the same size as a standard iron (24mm) and can be considered as the light version of the GP201.
It has 2 heat settings, a carry bag, a swivel cord but also our exclusive Sense Technology.
The SimpleTouch will turn on as soon as you click the plates together and you don't have to wait to heat up. Also if the iron senses no motion it will turn itself off after 35 seconds.