Sash depth matters for many reasons; strength, energy efficient, and noise reduction (just like a walls depth).
Also some manufacturers only use 1 lock in the center to pull the sash (presumably) tight into the main frame when it's closed.
But better window designs will use 2 minimum (sometimes 3 ) on taller windows. What this does is seals tighter and more evenly along the vertical sash line, and puts less stress on the hardware.
Also your better designed casements have only 1 lever at the bottom and when you lift it up or push it down it engages or disengages all 2 or 3 locks.
Also if you have an eye for detail you'll notice the one in the middle has triple weather-stripping, the other 2 only have double weather-stripping.
Try to understand this; the windows on the ends are really made to wholesale out to dealers, but the one in the middle comes straight from the manufacturer to the customer.
If you stop worrying about wholesale you can build a better window with a better design because your adding in better ingredients and components.
The sad thing is that one of the end windows costs more than the one in the middle, and the other end window is usually priced about the same as the one in the middle.
Who says you always get what you pay for, certainly not me.
