I put a hair across my main o-ring, and pumped down my system to 10" Hg. It took almost 10 minutes for the vacuum to fall below 5" Hg. So unless you make sure you pump down your system and check the pressure with the gauge at least 10 minutes later, AND before subsequent dives to make sure nothing got bumped out of place in the camera table, I still see a benefit for the electronic system.
Good point, indeed.
I have the non electronic version... seems like a solid piece of gear. Very reassuring, but: With that model, a STABLE vacuum reading is critical.
If the vacuum is changing, the housing is leaking.
If you start out at -10in/Hg and it "drops" to -5in/Hg the absolute value doesn't matter. It doesn't start to leak when it gets to 0in/Hg.
The ∆ indicates a leak, and if its leaking air, it is leaking water.
The point is, with a non monitored system, stability of the initial reading is key. Don't fool yourself into thinking a small change doesn't matter. It does.
However, be aware of temperature/pressure fluctuation.