This is so subjective like so many things it will boil down to hunting style and personal choice. I've used many on the market, including the Lone Wolf hand climber and numerous Summits, API's, Loggy Bayou's, and various loc-on styles.
There is no one answer. The Summit Viper is by far the most comfortable and easy to climb, but very hard to shoot out of with a stick bow. The Summit Open Shot (I have the Cobra) is comfortable and offers more shot opportunities but the arm rests still get in the way.
The Lone Wolf hand climber offers much more shot options, but with that comes limited comfort as it's basically a minimal loc-on style seat. I also though it was very uncomfortable to climb with. I'm 6'1", 240lbs and have been a weight lifter for 20 years. The angle and placement of where you have to put your arms was too tight for me and pretty uncomfortable to climb with.
My favorite was just the base of the old Loggy Bayou stands - I hugged the tree instead of using the climbing aid. Fastest and easiest climb for me, but not safe. In fact, I fell from it, and my Dad fell out of one as well to serious injury. So...it went to the rack for good.
I like the API's as well, but they are not quite as solid as they have a narrow notch that hits the tree.
After all that, I choose the Summit open front style (there have been many names and variations over the years). It's the best for me when weighing the variables. It's very comfortable and solid, it's relatively easy to climb with, it's quiet, and it does still allow a decent range of motion for a longer bow. For stick bow hunting - it's hard to beat a loc-on or ladder stand though, but sometimes you just need a climber. I still do 90% of stand hunting from a climber.