Wind-Up is a bit of a cult favorite.  He had a decent size fan base prior to being released, and those who were so fervent about him have maintained.  I think the recent single pack release will make him even more popular.

Wind-Up, despite being the character who should have been in the Tower of Time AP, is a Tech Element Newlander and ties in very well with the "tech" concept.

His Base Upgrades touch on the Primary and Secondary while introducing a Tertiary Attack.  This makes him fairly well rounded, but quite vulnerable when you make a habit of Winding Up...When "unwound" Wind-Up is really slow, hence the vulnerability.

If you are concerned with that, you will be inclined to take the Winder Path.  This is my path of choice just because I like the look of the Windup Punch.  The big draw to it is Power Crank that pulls in enemies and deals extra damage.  The logic of myself and many others is simply that this will allow Wind-Up to do what he does best, Windingup, AND totally compensate for the lack of speed thanks to the combo of Power Crank and Auto Wind Up, which winds you automatically when you take damage.  It works quite well and then you can continue to Power Crank, or use the charged attack Windup Punch to deal some very HIGH DAMAGE 120-180.  Again, my main draw was offsetting his weakness (being unwound) and just plain and simple I think the Punch is cool.

However, the Soul Gem, Spring-Loaded Crank,, takes away some of what should have made the Winder Path special.  It gives him +15 Speed, but also automatically winds him up while running.  So, if you took Toy Box , but liked to use your Wind Up abilities, when you start to flee any surviving enemies, you are simultaneously filling your meter to Wind Up again.  Granted, it is still faster (slightly anyway) by way of the Winder Path, but those who make it out to be the better path, or emphasize that aspect as a shortcoming of the Toy Box Path are wrong.

Granted, just comparing the two paths there is no doubt that Winder is superior to Toy Box in terms of helping you utilize the secondary attack Wind Up.

The catch is that the Soul Gem compensates for that deficiency and makes Toy Box a viable choice.

While Winder should have been a juggernaut for those who love to Wind Up, the Soul Gem coupled with Toy Box make you compare the numbers.  Since the only real stand alone upgrade to Winder is found in the Windup Punch you have it's very impressive 120-180.  But, while Toy Box doesn't deliver the big hit, it delivers a lot of smaller hits.  Just going with a 1-2 of 34 and 42 you are up to 78 and can fire it off again without charging up to jump to 156.  Perform Crash Cymbal while fully wound up and assume we get non-critical hits and you could have upward of 212 by the time the 6th hit rolls around.  Furthermore, you have access to an upgrade to the tertiary attack.  Holding that button will let you fire off 9 Toy Gun missiles that do 18-27 damage 8 times.

That said, it really comes down to how you like to play Wind-Up and what you prefer aesthetically.  If you like the old toys with cymbals or have an affinity for suction cup guns, take Toy Box.  If you prefer the comical wind up boxing gloves go with Winder.  On the gameplay side if you like the primary and an idea of a longer ranged weapons go with Toy Box.  If you prefer to use the Wind Up ability and like the massive damaged from charged one-hit attacks go with Winder.

For rookies I would hands down suggest Toy Box.  I am inclined, with the Soul Gem anyway, to think that it is the more well rounded path.  That said, I still like Winder, once again, primarily for the animations and instantaneous refilling of the meter.  It would have been nice to have the Soul Gem be an Armor Boost that would then keep the Winder Path dedicated to "Attack 2" and Toy Box for "Attack 1 and Attack 3," but oh well.

Bottom line, both paths are good.  The Soul Gem really does serve to offset some of the downside to not taking Winder and makes Toy Box just as good of a choice.  Ultimately I truly suggest you go with which attacks and aesthetics you personally like best and call it good.