Exactly the same as Bilco here
You will obviously get less miles out of them, but proportionately, they are that much cheaper as well, so the end cost per mile of each type is about the same IYSWIM.
Knobblies rarely need balancing, which is good.
Knobblies will slip easily on wet white lines and ironwork like manhole covers (sorry, person of non descriminate sex covers) and tarmac banding etc, but you very soon get used to that and it can be rather fun, deliberately getting the back loose as you crack it open on a bit of steelwork
Also knobblies are lower speed rated......TKCs for example are only rated to 99mph
They won't immediately fall apart at 101 though
They WILL however, start getting cracks around the tread blocks if you do a long autobahn journey two up with luggage at about 110+ cruising speed (including an inevitable 'lets see how fast we cab do two up' moment

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TKCs on the Autobahn south of Munchen
For day to day road use in the UK though, that won't ever cause you a problem and before some berk says it, it doesn't matter that the tyres are rated at a lower speed than the bike will do for insurance purposes...GSs come out of the shop brand new with them on
(If a TKC shreds on you at 130 though, it might be a slightly different story

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I run TKCs permanently on my 1150GSA, but would be happy to stick on K60 Scouts as Bilcs says......it's just that the last few times I've put new rubber on, I was about to do some long miles offroad so went for the TKC instead.
TKCs are also easier to fit yourself, as they have softer side walls
First ten minutes out on them, you'll hate them.....it'll feel like you're riding on marbles, but after 100 miles the sharp edges buff down a bit and you'll be grinning
