I just got a Diana F+ -- found at a thrift shop.
I don't know about the Holga, but this Diana has 4 F-stops. Since I didn't get a manual I don't know what those F-stops are but I'm guessing they're about 22/11/5.6/4.0. The lens is plastic. On some Holgas you can get a glass lens.
The shutter speed is fixed at whatever it is - maybe close to 1/80th and it has a "bulb" setting where the shutter stays open as long as you hold it.
This camera has zone focusing and a plug-in flash that sits on top. I believe the Holga has a built-in flash.
Also, the film back on the Diana slides on and locks in place. I think the Holda is held on by sliders on either side. Looking at the Diana it seems less likely to have light leaks around the sides.
One more thing, the Diana has a tripod socket.