hi there
this is a good question, as im currently playing with some units, (trying to get them working again after 30 years in the shed unused ? )
But I can tell you most bantam racers on here, have unberleaverbly fast reving Bantams, to cope with the astronomical revs and the speed at which they reach them, they need counters ahead of themslevs as they are no getting on an you now things tend to slow doewn as you get older, !! anyway the type your talking of is in my opinion useless, but an ideal unit as it gives the old un's time/chance to change gear before the motor distroys inself beteen gear changes,
but seriously, some say its to do with the age of the average Bantam racer, slower reactions so a unit infront of itself sounds ideal ??
I dont have one, as I prefer the much more accurate Kart type units, and this is absolutly nothing to do with the fact they cost less than a £5.0er from ebay.!!!
seriously I prefer analoge type as they look more period than the digital type. hope that helps ? lol
regards Derek