Seen them in use and indicated takes both pulls and dropbacks ok, also seen the Billy's Backbiters which look a bit bulky to me as well as being a lump more expensive.
If possible I would always use a float for indication as it's more immediate indication as long as its watched carefully.
The thing with backbiters as I see it, is you're not gonna use 'em for your carping or tenching etc. Unlike a decent set of front alarms which will cover every use , coupled with bobbins or drop-offs.
Only my opinion of course.
There is a video on You tube. LEDGERED DEADBAITS WITH MICK BROWN. He is using Shimanos ashe says the baitrunner is so smooth and heavyish swingers that indicate both runs and drop backs. Worth a look.
I have always thought that the sudden change in line tension when it is pulled from the clip is responsible for a lot of dropped runs from Pike and more so from Zander.
After many years of battling with Fox PS alarms, it is my intention to switch to normal quality front alarms combined with a basic rear drop off arm this winter.