I'd guess what ever works well will mean it's too visible to light fingered scrotes to be left on if you leave the bike
To be honest not even bothered on the bike as if the roads open, then I'll be able to filter on the bike Might be usefull if you're around Sheffield though
Probably better taking it off when not needed. Its going to be useful when travelling in Europe to, hopefully, avoid some of the French/Italian motorway holdups. I know one can usually filter but, given time, I'd rather avoid the block and use the N roads.
I use one in the car and its OK but the data is often not very up to date. Never bothered on the bike as most of the time its going to be quicker to filter through jams than frig about on a diversion.
I've got my GTM 11 (bigger unit) Velcroed to the back of my 2820... Rarely use it on the bike, but never venture out on the the motorways over here without it... It has definately saved us from sitting in traffic several times now...