Disclaimer: I sell these and many other brands of kites.
First of all, welcome to kiteboarding! Good to see that you're doing your homework first before just jumping in. Trainer kites are one of the best ways to ease your way into kiting. I have not used the Flysurfer, but I've flown the React quite a bit. I also have used the Slingshot B3 even more. I think that like juandesooka said, it will mostly depend on what type of kite you intend on using: Foil or Inflatable. Without getting TOO deep, here are the pros/cons:
Pro: Works well in lighter winds b/c it weighs very little; more resilient to crashes b/c there's no internal structures (bladders) to rupture; good power relative to size.
Cons:Tends to "taco" in light winds and fall down; set up is completely opposite from the way most kiteboarding kites (inflatables) are set up; will float for only a short time before becoming waterlogged; need to buy your harness in order to try it out "hooked in"; relaunch is unlike a relaunch for inflatables.
Pro:Depowerable by pushing out on the bar; relaunching it off the water is exactly the same way you relaunch an inflatable big enough to ride; set up is exactly the same as a full size kite; carrying bag actually transforms into a harness for flying the react; React comes with a $50 gift certificate towards a lesson that any OR dealer will honor.
Cons: If you can't quit slamming this kite into the ground, you may eventually rupture the bladder (this may be a hint that maybe you should take up golf instead
); not as powerful as the foil.
I didn't keep that as short as I'd hoped, but maybe it will help you sort it out. Bottom line: if you think that you're going to be an inflatable rider like 99% of kiteboarders, then I would pick the React. If you think that you're going to be a foil rider, then I'd pick the Flysurfer.
Either way, getting a trainer kite and flying the crap out of it until you're able to control it instinctively is a great start. Getting lessons from there on before buying any gear is the next best step. Good Luck!
EDIT: Nicely put, Coloradokiter!