When it comes to kneeboards, its a wide wide world of choices. You can get multiple different kneeboards for all sorts of purposes, from holding your ipad, to a traditional kneeboard.
My thoughts on this subject are simple. Keep it simple.
The kneeboard that I use is made by a company called Sky High Products and is called the Strato kneeboard. Originally designed for helicopter pilots who don't have lots of time (or hands) to write, it is a modular kneeboard that you can attach additional loops, pens, writing tablets, batteries, and flashlights to.
The best part about this kneeboard is that it is small, and in the cramped cockpit of a training aircraft it doesn't interfear with the controls freedom of movement. It is small, and easily fits into any flight bag or backpack.
I consider myself an essentialist, meaning I only like to bring the items with me pertinent to safety of flight. A headset, kneeboard, handheld, survival kit, cell phone, kneeboard, batteries, and charts.
This kneeboard is an integral part of keeping my flight kit small and letting me easily access all the things that I need to when I need to get to them, instead of rummaging through multiple bags and backpacks adding unneccesary weight and time to my flight.
I personally endorse and reccomend purchasing this kneeboard, as I have been using it exclusively for the past 7 years and have yet to encounter another kneeboard that compares.