G700 was a top end laser gaming mouse. Battery life sacrificed for maximum performance. On the other hand, your mouse sacrifices performance for maximum battery life.
I smell excuses.
I am thinking it's more like the G700 is a top end gaming device. Hence, it might take too much time and effort to optimize such a short run, niche product for low sleep current.
Designing and coding for low sleep current is device specific. It is one of those things a consumer takes for granted, but it is a total PITA and requires some work with the datasheet. You can't just code it in C with your favorite compiler. There's a big nest of decisions that has to be made, correctly, starting from the start.
Even if the one mouse draws 10x the current while in use, that wouldn't necessarily be noticeable over the life of the batteries. If there's a huge difference you can bet it's the sleep current.
It's not "excuses", wraper is absolutely right: it's deliberate design decisions.
In normal wireless optical mice, the sensor goes into sleep mode after a period of mouse inactivity (somewhere in the ballpark of 10 secs, IIRC from my last wired mouse), waking up briefly every 1/4 second or so to check for motion, and waking up if there is. (You can see this because the LED starts a slow blink.) The downside is that if you haven't moved the mouse in a bit, then there's a delay before the mouse pointer actually starts moving. In normal desktop use, this is absolutely no problem and essentially unnoticeable. Additionally, the wireless receivers use low-power modes.
In gaming mice, where a 1/4 sec lag could cost you a shot, wireless mice totally forgo sleep, and stay fully awake the whole time so that they react instantly. On top of this, they use faster sensors, which use more power to begin with. Finally, they use different wireless that uses higher polling rates and no sleep. And that's why wireless gaming mice have miserable battery life compared to their regular counterparts.
I have the non-gaming equivalent of the G700, the Performance MX. I do notice the tiny little lag when waking it from slumber. (I can't observe it directly, since the Performance MX and G700 do not use an LED light source, but infrared lasers.)