Mens lacrosse heads have pockets so that when you get hit its easier to hold the ball, but because women lacrosse is a none contact sport there is no pocket and cradling is different.
The x10 is the newer version of the xcalibur the x10 is 10% stiffer then the xcalibur.
Yes the boys head is thicker and has a much deeper pocket
The netting, size, pinch, and durability of the frame.
Lacrosse heads for defense tend to be wider and easier to catch with, offensive heads tend to be narrower so that the ball stays in when being hit and cradling more often. It also helps with shooting in some situations for offensive heads to be narrower.
Stx lacrosse heads DO fit on brine shafts.
Lacrosse monkey provides a wide range of lacrosse heads. The products are of high standard for a product sold at a standard retail price. eBay provides many second hand heads in mint condition for a cheap price.
Almost all lacrosse heads are compatible with other shafts, so that you can mix and match them.